I did not like the way my TIG foot pedal was configured, so I used an idea I got from a drum pedal. I mounted the original pedal to a piece of aluminum plate (this was actually an old aluminum threshold that I cut down to a 4" width), then hinged another piece so it would depress the TIG pedal. The long bottom piece is about 18" and the top piece is about 12". Works much better now. Pedal doesn't slip and I actually have more control over the variation in power. Build would also work on similar variable power pedals with similar configuration.
I used aluminum because that's what I had on hand. You can use anything including plywood for this. Just make sure the top plate that you set your foot on is rigid enough not to flex when you depress it. Also, my original pedal had some ridges on it. I suggest that you do your build, set the original pedal on it with the top plate about half-way on the pedal. Then depress it fully. This will cause the pedal unit to move slightly as the top footplate finds its position between two ridges. Mark your pedal location and screw it to the bottom plate.