harbor freight - welding blanket - cut to size- done!
Works, but will eventually give you splinters
Plus one on just using a welding blanket. I've had the same cheep over from harbor freight since 2013, and it hasn't given me any issues. That's probably a sign that I don't get near as many trips in as I need to.
Amazing deals on this 4Ft X 6Ft Fiberglass Welding Blanket at Harbor Freight. Quality tools & low prices.
I think one could buy a $7 tube of silicone RTV and squeegee it onto your HF welding blanket which would make it easier to clean and non-splintery. But the Fireside Outdoors "ember mat" is awfully nice and ready to go.