I am doing my hearth in 12"x12" dark porcelain tiles and had a thought that I might cut a 12x12 tile in a contrasting (lighter) color into quarters and set my stove legs on top of those resulting 6" squares. They would act kind of like coasters. They would not be grouted into the hearth. I'd just set them on top of the finished tile work and then set the stove on them. The idea would be threefold: 1) the lighter-colored "coasters" would make the black cast iron of the legs "pop" a little more rather than just blending into the dark field tile. 2) the coasters would serve like kind of a sacrificial hearth. They'd get scratched instead of the permanent tile 3) if I ever get a bigger stove, I could just move the coasters to match the new stoves dimensions, as they are not permanently fixed to one spot. But I'd need to put something soft on the back of them so that they would not scratch the permanent tile themselves. My first instinct is to hot glue some cork sheet (like bulletin board material) on them, but that is combustible right? What is thin, soft, and non-combustible that might serve as a backing for such "coasters"?