How Did You Build Your Stance Mat/Platform?

I did a search and there are some threads about the mat people are using to stand on, but what are some ideas to make the stance mat height level with your simulator pad? The GSA PX2 is a little more than 3 inches tall, so how have others dealt with it? Plywood, building a frame from 1x2's, styrofoam? Could you buy a fiberbuilt rubber mat system (for example) and cut out a 1 x 2 hole from the rubber?

Also, with an elevant stance mat, it seems like using a 4x4 or 5x5 fiberbuilt mat that's elevanted 3 inches in the would give a strange feeling and throw off balance. Thoughts?