I made a decent sized mat for the basement of my old house. I think I had enough material for a 15x15 mat for $150.

Basically,

I caulked a bunch of sheets of 1 1/4" or 1 1/2" (I can't remember) thick styrofoam insulation together to form the bottom layer. It's the blue stuff they sell at Home Depot.

I then put a layer of 1/4" thick carpet padding over that. I think I caulked that too.

I then covered that with elmers glue and put a canvas drop cloth down. Bam. (I also had a vinyl drop cloth that I put over it when I wasn't using it)


I could grapple and practice throws with this thing which was layed on top of concrete. It was a pretty nice mat.