I'm building a countertop out of air dried (5+ years) english walnut. My stock is about 86" long, 8-10" wide and 4/4 thick. My wood rack must have sagged slightly because the boards have a 1/4" bow at a spot about 1/3 of the length. My jointer is only 6", and my planer 12".

I don't really want to end up with 1/2" thick wood and besides I'm not keen on building an 8' sled for my jointer to flatten the wood.

Since only one side is going to be visible, and since the top is going to get covered in a 1/8-1/4" coat of clear epoxy resin (preventing exposure to moisture), I'm thinking of just gluing the walnut down to a substrate of mdf that is clamped tight to my workbench. By alternating the boards I can keep the "sag spot" off the same place on the mdf, and hopefully the mdf will keep it flat enough for the epoxy to make up the difference. I tried clamping the walnut to my bench was pretty easily able to clamp out the warp.

Thanks for the input.