use CA glue, or a staple gun of some sort. some people use hot glue and it works, but depends on the application i guess. i'd recommend using the matting to add strength to the pod itself. at least 3 layers or so. the filler is just to help smooth it out, not really add any structural integrity. stay away from the filler with the glass in it when you're ready to sand it down to smooth it out. i find that it's harder to sand than if you use 'gold' filler