I built mine with 2x4 for the frame and 1/2 plywood. I also recommend getting some of these, makes moving the bench around the garage super easy
Woodtek 163703, Hardware, Casters And Glides, Furniture & Cabinet, Workbench Stepdown Caster Set, 4 Each https://www.amazon.com/dp/B009ZDDLVI/ref=cm_sw_r_cp_api_hCq7xbG330E70
How about these, or a variation thereof?