Product review (2 stars): may work for you, but beware...
Bought these under the false impression they were fireproof and stiff, only to discover they melt and are about as stiff as a napkin.  Also, very slippery on our enameled stove top, easy to move which will cause the interior edge to buckle and get too near the flame (and melt more).
We will try to use them, but I'm wondering if just cutting up some tinfoil sheets would work better.