I use one layer. I wait until I have turned and top stitched the cozy before sewing the X through all 3 layers. It isn’t hard to do, and it looks very neat that way. And I have made hundreds with Wrap N Zap without issue. If anyone thinks the Pellon lawyers have not exhaustively insured the Wrap N Zap won’t catch fire when used in the microwave, they don’t know large companies and lawyers! With the specialized batting it is perfectly safe to use in the microwave as indicated. But then again, some people prefer their own “research” to that of scientists and engineers.