Hello
I would make it like this if using wood ,
I would be using 5 or 7 ply Grade " A " plywood ,cabinet grade.
so you can cut true sizes and not have to worry about finding 1 x 2 or 1 x 3 ,
that were any good.
This would take care of any trouble of warping , checking etc
if you has been looking a wood lately ,all I see is prime grade prices for number 2 wood.
Or just make it out of steel like BRWESTER 's
Which I really like a whole lot