It’s taken me a while to get this DIY project to the final stage, because I had to keep buying more marbles. The zip-lock bags are re-purposed, as well as the sponge. The piece of board is just a re-purposed cheapie painting. You could just use a flat piece of custom board or plastic.
You can either just stand on this, or move your feet around, in order to stimulate the pressure points on the soles of the feet.