Try making one and see if the glass is stable. Because the edges are not round or square, they might not be as large as the bottom of the glass. And please let us know if they work as coasters. You might start a whole new trend.
Will see I have time this weekend to give it a whirl. :-)
That's something I hadn't thought of doing with them, I suppose you could use felt or towelling for the back and not stuff them..
I've made one of them - it is in projects. I suppose they could be used for coasters.