Not sure if you are replying to me, but rough cut straight from the mill is green so it needs about a year per inch to air dry.
We actually have both. Amish saw mills that cut rough hardwood (usually pallet material but you can place an order for anything) and lumber yards that sell regular dimensional construction materials at low prices.
Plywood makes much more sense for something like this. I used 5-6 ply birch (not Baltic birch which is now close to unattanium) but construction grade would work ok too.
I tried straight pocket holes for this. Not quite strong enough so you see the counter sinked wood screws on the edges that I added after the fact.
I suppose if one really wanted to go above and beyond, box jointed hardwood would be neat, but I lined my boxes with 1/4 inch rubber floor mat material (for both electrical resistance and as part of cell compression) and would want to negate movement.
You can see the lining here:
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