I made one for myself a few years ago. I used a sheet of 3/4 thick plywood, 36 x 76. I covered it in several sheets of heavy weigh tin foil, cotton batting and topped it with cotton duck cloth. Everything was stapled to the underside. Then on the underside I made a set of rails so that it could sit on top of a banquet table. When I want to use it I set up the table and slide the ironing table onto it. I also use PVC pipe on the table legs to adjust my table to my height.
Over the years it's gotten grungy, but I didn't want to rip it apart and redo it......it was a busy summer that year. So I got out my carpet scrubber and used the hand attachment to scrub the top. I worked so well. I had it in the sun to dry and the top tightened up again like it was new. I think this summer it'll get redone, but I'm thrilled that it's lasted so long.