Well, as usual, the answer is not black and white.
In general, if you carve a frame from dry timber, your joinery will remain as tight as the day you raised it, as it should be done moving. But it's usually easier (sometimes much easier) to carve green timber, and drying can be impractical, so you have to weigh the one against the other. The species of wood can greatly influence the decision.
I work primarily in white pine, and I've always worked it (relatively) green. This is due primarily to the fact that as a professional, I prefer not to tie up a lot of money in inventory waiting for it to dry. I do have the option of buying dried timber, but the added cost doesn't seem justified. That's my opinion only.
White pine works very well when green, and is well behaved as it dries. By well behaved, I mean that it does not shrink drastically, in contrast to oak or douglas fir. It also tends not to bow or twist very much, in contrast to, say, red pine. That said, dried white pine is not nearly as difficult to work as dried doug fir.
If your are air drying it yourself, then you will probably still get some checking, and unless you wait many years, it will continue to shrink some after you cut it.
Not an exact answer, but hopefully worth the $.02 I contributed to your project :-) Good luck! CB.
