Go to Lowes or Home Depot and check out the Simpson brackets for building a workbench with 2x4s.
I have two benches with supports in the middle and two shelves. I toped them with two layers of
3/4 " ply and 1/8" Masonite. Solid as the Rock of Gibraltar. I did not build these as building benches
and cannot attest to their flatness. You could go that route if you want. Do make sure everything is square
before you start putting in the screws.
KW_Counter