Eating your ice cream cone from the bottom (or, sudden changes in process)

So, it's been a while -- I've lurked, just haven't posted in almost two years. My writing's going pretty well. I've completed two novels so far. One is your standard "under-the-bed book", aka "desk drawer book", aka "I would have to spend enough time re-writing this that I might as well just write a better one"; the second has just been picked up by a reputable agent; and now I'm embarking on a third, the ideas for which have been floating around in my head for about six months now. I've been world-building in the form of scrap notes and writing small segments of the beginning. And, of course, now that I've got an agent, I want to go full speed ahead.

The weirdness I'm having is that it wants to take shape exactly backwards from how my others have.

Previously I'd start with a concept, get characters to form around the concept and get plot to form around the characters: I'd put together a very rough external plot summary and then just write as I went, and the micro-plot would fill in spontaneously -- sort of the way Raymond Chandler described his process, not knowing whodunnit until you get there.

This one has started with characters and tantalizing, dreamlike bits of world detail. I have a great feeling about it; like it represents a certain maturation of where I'm going with all this writing stuff. I'm in love with my characters. It's deep-brain material for me instead of trope play. But at the same time I'm not sure how to structure my work. I'm having lots of fun worldbuilding, but my actual narrative currently consists of a bunch of little disordered scraps and paragraphs of scene.

I have pictures in my mind of the relationships and scenes at the heart of the book, and a sense of the ending, but not nearly as much sense of the concrete specifics of how they got there.

The outlining techniques from the Uncle Jim thread are doing me some good. But I'm mainly curious to hear from a range of other writers. Has anyone had this sort of flip-flop in their creative direction? How did it go for you?

And finally, what are some of your techniques for getting a clear sight on the beginning when you know the end?

Hmm! I didn't think of setting up the resolution.

The stuff I have clearly in my mind consists of Main Middle Event 1, the end-of-first-act thing that means no turning back for the characters, as someone was talking about in the other thread... and the climax, at least of the interpersonal arc.

I think one of the oddities I'm dealing with is that the external plot is basically heroic (find the macguffin, save the day) and the interpersonal arc is semi-tragic. Hmm, I suppose that's not so odd, now that I think of it.

Another thing adding to the difference is that my previous long fiction has been urban fantasy -- take modern world, melt with hairdryer, re-shape with round-nose pliers, add some collage -- and this one is an actual bona-fide otherworld, with whole continents and languages and magic and industrialization to sort out... so I suppose the "start from point X and plow forth in any direction" is not quite so possible; I can't use my old props bin or grab extras from Central Casting.

I think the reason I'm wringing my hands over this one is that I'm already too attached to want to risk bailing out. Of course there's always a risk. I think I'm probably going to find a plan of attack, whatever that plan is, by doing what I'm doing now: outlining, notecarding, sketching out material for the idea drawer.

I'm going to think over the resolution, and maybe try to crack it. This could be really good for me as a writer, as I usually find getting past the climax to the tie-up is the most cumbersome part of any book, and writing it first might get me doing something I've never done before...