Hi, excellent thread - I've never seen one of those before.
Since bushcraft emphasises working with natural resources, I have to say I can't see the need. Cut and roll back the turf, set aside, keep damp, replace when you're done with the fire ?
This looks like a response to laws restricting campfires or forbidding digging in national parks.
If I wanted to improvise one in the UK, it looks woven, is presumably a heat resistant fibre, so why not try an ordinary fireblanket ? With some earth on top it probably won't overheat and take any damage in use. Exotic would be 2 old fireblankets stitched together with some sort of insulation in between.
Cheers, Alick