I don’t know how many people do this, but it can sometimes be valuable. And it’s very useful when the story decides to change itself entirely anyway.

1) Know what scenes absolutely strike you.

If a story starts with a powerful scene for you, it’s not always necessary to decree that the scene must happen in Chapter 42 between scenes A.ii and A.iv, with these characters having discussed the meaning of life and had tea just beforehand. Outlining like that is life’s blood to some authors, but not to everybody. And it gets completely screwed up when the characters do start to demand a more active role in the story, and change things around before you get to Chapter 42. And if you get too caught up in outlining the story, are you ever going to write it?
The “criteria” for a scene can be as flexible as you like. If a scene is powerful, claims your attention, and makes you really want to write it, I personally think it’s a more likely candidate to be in the story than the “Well, this doesn’t thrill me, but it should be there” scene. Remember, outside of genre requirements and the story being written in a way that doesn’t totally puzzle your audience, there are very few rules for where you “should” begin or “should” end, or what “should” be in the middle. I think a lot of the clichéd beginnings and endings I see are because people decide there’s some requirement to start with a panoramic view, and, oh, here’s the infodump on the character’s childhood, and, oh, here’s the part where we find out she was abused, and, oh, here’s the part where she runs away from home, and here are the sex scenes, and there’s the confrontation with the villain, and there’s the happy ending where she’s crowned queen.
Why not aim for a scene that strikes the “MUST WRITE” chord in you, rather than for things that most fantasy books already have?

2) Leave character roles undefined.

I am convinced now that the reason a lot of fantasy romances feel forced to me are not just because they’re romances, but because the author has made an executive decision before the story as to who must fall in love with whom. Many authors persist in shoving people who have no chemistry and no compelling reason to take note of each other together. In some cases, this means that better choices get ignored—maybe the heroine’s sidekick would actually be a better husband for her than the designated “hero”—but more often it means that the author resorts to contrived situations to torture the characters into infatuation, because she has no other idea why they would look twice.
Take the book I’m reading now, Song of the Beast by Carol Berg. I loved her Rai-kirah trilogy; this book is set in a different world, and was published later, but written first. And does it ever show. Whereas the Rai-kirah trilogy largely ignores romance because the characters are concerned with doing other things, and rightly so, this one shoves the heroine and the hero together willy-nilly. Their backgrounds are very different, and the heroine has good reason (to her at least) to hate the hero. What “romance” is there depends largely on the heroine’s childhood infatuation, which has somehow endured for twenty-two years, the hero being so perfect no woman can resist him, and some touchy-feely moments they share because, of course, there’s no other way for them to escape danger than by kissing each other.
This is one story where it doesn’t really make sense for the hero and heroine to fall in love, considering what their goals are and what their personalities are like. Yet there they go. Every movement is predictable, because they’re not growing and changing into people who could associate with each other; they’re staying the same, and the author is simply changing their minds for them. Though I like the story otherwise, the romance is getting in the way. It’s clumsy, and it is obtrusive. Song of the Beast has the potential to be a story like Rai-kirah, it shares a lot of the same traits, and the romance should have been cut out altogether.
Why do you have to have a designated love interest? Why not start writing, and let the characters decide who they’re going to fall in love with, if they’re going to fall in love with anyone at all? For that matter, why decide beforehand that this person is the hero, this one is the villain, this one is the foil, this one is the comic relief, this one is the spitfire teenage runaway, and so on? Trying to force them into stock roles creates stock characters. About the only choice that you must make is whose viewpoint you’re sharing in a particular scene or chapter, since bouncing wildly in and out is a good way to lose your audience. But the viewpoint character isn’t always the hero. He isn’t always the villain, either.
Just write the story, and the most wonderful surprises can come your way—surprises which are hard to come by in strictest outline form. In the worst cases, those surprises are not only nonexistent for you, but nonexistent for your readers, enabling them to predict everything based on what they’ve seen in other books.

3) Leave off the focus on the ending.

Another way in which books can feel contrived and rushed is the author’s insistence that it end in triumph, or tragedy, or Character B marrying Character A—whichever way it “has” to end. I’ve seen “Know your ending” quoted as one of those rules of writing that are as inflexible as rules of grammar. Don’t know it, runs the mantra, and you will write a book that is impossible for anyone to understand.
To which I say, like the dignified adult I am: Uh-uh.
Letting the ending be your taskmaster is the worse problem in my eyes, because so many people don’t even see it as a problem. If you start writing a story that has an open ending, and it turns out badly, you can always go back and rewrite, and you’re more likely to know what you don’t want, now that you’ve seen one of the ways it might turn into a dead end. Write an ending that by god is going be the same ending regardless of what unexpected little monkey wrenches throw themselves into the story, and you might find yourself trapped into sticking with it to the exclusion of all else that is good.
There’s a lot of slagging on middle books in fantasy series as uninspired, uninteresting travelogues, with all the action happening in the beginning or ending book. I think I’ve read more series where the ending book was the problem. The author sets up a prophecy to be fulfilled, and while I’m actually more interested in how the characters are dealing with events in their personal lives, she Goes and Fulfills the Prophecy. These two characters are getting together, never mind that they spent the majority of the series apart and grew into different people, and so They Get Together. I am looooking at you, Tad Williams and Anne Bishop.
Perhaps part of this is fear of disappointment. The author comes up with an ending that makes sense for the original draft, so she clings to it and nourishes it even as the draft changes, like all living things do, in the process of becoming alive. What might happen if she changes the ending? Maybe screaming chaos. That mere “maybe” is enough, I think, to keep authors shoveling food into that bloated, squalling baby’s mouth, even when the story itself is crying out for a different ending to be fed.
And now that I’ve really overstrained that analogy, let’s go somewhere else.

4) Let the story be the boss.

Not the plot, not the setting, not the characters. The story, which is born of their interactions.
Plot, setting, and characters are common things for outlines to emphasize. This Plot Device goes here. The backstory of the setting that the author spent so much time crafting comes into play. The characters are This Way because they’ve been cooking in the mind of the author for years, so when she puts them in the story, they are damn well going to follow the outline.
But what happens if you start writing, and it turns out that the plot doesn’t fit those characters anymore? You might think this can’t happen, but let the author get too bound up in her world-building notes and it does, oh it does. You may recognize the voice of experience here, and you would be absolutely right. I had a darling plot that I tried to rewrite two times, and both times it was absolutely the wrong kind of thing to attach to an intelligent, self-knowing hero who would have seen through the main “villain’s” machinations in two seconds flat. Neither as third-person with many viewpoint characters nor as first-person did it work, and I should have simply gone with the many new ideas that suggested themselves to me instead of binding myself to the old story irrevocably.
For setting, it’s the old problem of “I love this place” versus “What does the reader need to know?” If the reader doesn’t need to know the entire history of the Pirate War to make sense of the story, do not include the entire history of the Pirate War. Worlds are beautiful and fun to create, but unless you’re writing a game setting or one of a very few other specialized non-fiction genres, you’re writing a story, not a guide to the world. You can point to the guides to fantasy worlds like Middle-earth and Pern if you want, but in every case they came out only after the world became popular through the novels. Not before. If you can’t give people characters to care about in the middle of that Pirate War or living after it and being affected by the consequences, why should anyone care about the dates or who started it? Saying in the outline, “And here they learn about the history” is also a cliché in fantasy now, the scene where the Wise Old Mentor sits the Young Dunderhead Hero down and tells him everything he needs to know, to the boredom of many experienced readers.
Characters are a special matter, since so many outline-less stories are character-driven. Yet, at the same time, you can’t let them write the story alone, or you’ll succumb to the temptation to make them perfect, let them conquer every challenge, and have their happy ending without effort. (What character would really want to lose his family and go adventuring across the world?) The hero of a story isn’t the only one who matters; the people all around him are tugging and pulling on him too, affecting and being affected by his actions. The person in your head who is very brash and self-confident might be less so when he gets slapped upside the head by the plot or a feature of the setting that you didn’t apply to him in the character profile. Keeping them the same because the character profile or story outline Says So, when there’s been no alchemy of them with actual fiction yet, is a guide to contrived scenelets. (See point 2).
Writing with an outline is one way to do fantasy. It’s far from the only way. And I suspect a large part of the reason more people don’t write without one is due to fear of what might happen, or a desire to obey writing “rules,” rather than experimenting around and seeing what’s best for them.