I picked up two "slightly imperfect" (their description) unfinished under counter kitchen cabinets at a local discount cabinet place. Mounted a solid core door on them. I build with magnets so I put my mag building boards on the door. Works like a charm, workbench is at the right height plus each of the under counter cabinets has four drawers for storing "stuff". The solid core door is exactly flat. Only drawback is the door and steel building boars make a VERY HEAVY combination but it is rock steady mounted on the sink cabinets.

Works for me

Dan