Hallelujah. I've been trying to figure this out for years. I have never read a how-to that explained how, or why, you could or would create a custom layer.

I've been hacking the complete source code for Expressive on LJ the whole time, as it was the only thing I could figure out to do. Somehow, none of the how-tos made any sense. So, on the assumption that I'm not the only one that needs it explained with a different logic, and because I might need a reference point when I've forgotten, here's how (and why) it's done:
( Many people reading this already know how to suck eggs, but, y'know, for the rest of us )
That's it, job done. It really is that simple. Once you've got your head around it. The taskflow is unintuitve, there's nothing telling you what to do (or, perhaps more importantly, why), and the pages don't link to each other well.

It's no wonder I could never figure it out. Still, now that I have, I can A) add a few extra bits to my sidebar (like some text linking all the awards &c I've won) and b) maybe tidy this ramble up into something the dw_docs team can use.

But now now—gotta go get miss_s_b from work. If you know what you're doing, can you check for errors and/or answer my minor questions. If you don't know what you're doing, or bits make no sense, ask, as if I can't help someone else might, etc. And I'd like to figure it out.