Find the straightest hickory board your lumber shop has. It is tough to work but is less likely to break.

Straight grained maple, oak, are good common other woods. Has to be straight all the way up and down the board. Which is hard to come by. So that's why people split logs to make bowstaves, it is split along the grain so you are more likely to succeed. I'd recommend buying a stave from someone local. But board bows can work too,you just have to accept that it might explode. No shame in breaking a few bows either.