Theoretically a flat back and belly are most efficient. So if your growth rings are straight no real need to chase a ring. Spend your time chasing the best board in the stack and you'll be fine.
FWIW sometimes when people have tree staves, they "decrown" them meaning they flatten the rounded back of the bow until it's flat, much like a board.
Traditional Bowyers Bible 1-4, George's site as he mentioned, PoorFolkBows (Sam Harper's site), 4estTrekkers bow buildalong, there are other board bow buildalongs I cant think of right now but you can search them on here or search engine.