Can't do that. I'm making a lens board for my large-format camera.

Do I need to find a straight piece to start with?

Depends. Shoot everything at f64 and you might be ok.

It seems to me that 1/8" wood is pretty thin for for a lensboard. I'd just
as soon use a piece of aluminum. It won't be subject to seasonal
expansion/contraction issues, and will have no problem supporting a heavy
lens. Cover the front with leatherette and the back with flocking and it
won't look too bad. If you want to stick with solid wood maybe you could
laminate two thin pieces of wood together under pressure. It'll be thicker
than 1/8" but you could always rebate the the edges and the rear of the lens
hole if you need to.