Paul, from what I understand you need to get Flint Ridge a little hotter then Turkey Roaster range.
I'd experiment by burying it under about two-three inches of clean, playbox sand . put a 20# bad of charcoal on top and let it go till it cools down. Just try some small spalls and flakes and see what
happens.
20# doesn't cost that much and put an assortment of rock sizes in and see what works and what doesn't.