For years I used a pair of wood sawhorses and the old angle iron ramps from my old trailer. They were dangerous/failing and heavy so I replaced them with new alum ramps, and repurposed the old ones. Nothing was flat or even, and pretty impossible to clamp much to it, but it got me by for quite a while. I can understand how many people never get past something like that, especially if the need is very rare.
When I eventually moved into my new place with a big shop I built a table that was based on an old steel angle iron table I picked up cheap. Here is the old table already partly cut apart and getting ready for the 2" x 1/4" tube legs I added.
I had the frame powder coated. The top is 8 foot by about 28-30" wide 1/4". I put receivers on it to hold a vise and a ring roller and whatever else I came up with. Here is a shot of it all done.
The width was limited as I needed it to fit between my tractor and truck in the shop "garage". So I put 3 receivers on one side and made a set of "extensions" I could put in there to give me a bigger working surface when needed.
I just store the extension below when not needed so I can park the truck there. 3 pieces go into the receivers and then I have plates that drop in between and a couple flat head screws to hold them in place.
I would like to add some more hangers for clamps and such as they are all sitting on the shelf and it is a bit of a mess and everything falls off when grabbing them right now. I might do some brackets and bolt it onto the open side legs.