I gotta put in a bit. I make sapling bows like crazy, mostly elm, maple, plum, ash, and mulberry, and I have the best luck cutting and peeling the stave, and immediately roughing out the bow, or at least cutting the thickness down a bunch, then restraining it to dry.
So, say I cut a 2" ash sapling. I will take it home, look at the best side for a bow, and immediately hit it with the machete, chopping and knifing it down to 1" thick, a even thickness all along, which I roughly measure with a caliper or spanner of some kind, anything will do. I leave the handle 1-1/2" or whatever, but narrow the handle to aid in it not checking up a bunch while drying. Then I varnish/ coat ends and belly, (and back if you are nervous) and clamp or strap it tight and straight to a 2x4 to dry. Use shims and pegs where needed.
Saplings love to warp and twist when drying, much more than a split stave from a bigger tree, and a huge lateral bend is a bear to work with.
Put it somewhere to dry not too fast, maybe a cool place for a week or so, and then you can dry it really quickly, depending on temp. Bring it inside and put it somewhere warm.