Cut the cleanest straightest section of trunk you can, 6' long, and seal the ends asap with two coats of shellac. If you end up with a section that is 40" long or so, it can be split into billets which can be finger jointed at the handles later to make full length staves.
Once home, you need to split them into pieces 3-4 inches across the bark and store them somewhere out of the sun, wind, heat, etc. so that they can begin losing excess moisture. Then straight away, you can begin removing the bark and sapwood with a drawknife, bringing them to a single heartwood growth ring in the process.... and sealing that growth ring (the bow's back) with shellac when exposed.