yes you can cut a sapling now,, you can even take it down to a growth ring it you like , rough it out to the shape of a bow, coat the back and handle and fades,, let it stay outside in shed or something for a week or two( slow dry),, then bring inside for final dry,, hickory is pretty forgiving, and will make a fine bow if you get the moisture content down,, heat box might be good as you work on the final tiller before putting a finish on,,, this is a fine point, but if you cut the sapling and rough it out,, clamp it into several inches of reflex,,, it will keep it from twisting and give you a little better performance,, on the finished bow,,