Chriss, Go to the "How To and Buildalong" section. At the top of the page you will see Jawge'S(George Tsoukalas) website. He covers evewrything you will need to know about building a bow from a board or tree stave. Eric's site just about Geprge's has a handy tool you can make to help you achieve good tiller.
I'll have to disagree a little with Crooketarrow in that you can have a board stave. Any wood that is used full length to build a bow is a stave IMO. Billets are smaller pieces that are joined at the handle area to creat a stave.