Needed: Ideas for a cheap temporary Floor work surface

old used steel wheel turned upside down with the jack stand inside of it,is what I do outside

Or what the local U-Pull It junkyard here does. Two wheels, one upside down, the other standing on edge inside the other, welded together.

I wanted to kill 'em for doing this. Back when they started it wasn't unusual to go in and see Magnum 500's or rallyes welded together like that. But it's effective.