Ceramic glass is awesome on a platen. In the trade it's called fireplace glass and commonly available at every glass store. It's also common they charge you for at least a square foot plus a cut charge for each cut. I tried to find it myself several times where it was less than $50 a piece. I couldn't but that was before I got into selling it. It is NOT easy to cut this stuff on your own like common window glass. It takes a carbide wheel and you get one chance to score it correctly and then snapping it off is 50/50 of it breaking cleanly. I do occasionally cut a piece shorter using my diamond blade on the wet tile saw. That is a gamble every time as it is prone to crack.
2 really important things. If a piece of this comes loose at full speed, and it has for several guys, it's a really bad situation as you can imagine. I use JB Weld as it seems to have the highest heat tolerance of all the epoxies I have seen that are commonly available. If the epoxy you chose fails at around 210F, don't use it. Test it by boiling. I use a little ledge to support the glass in case the epoxy fails but I also have some platens that don't have the support.
When you glue the glass on, do not use a clamp. Let it float on the epoxy (a few air bubbles as possible for even heat dissipation please) and tape it place to cure. If you clamp it, you will bend it slightly and build stress into the glass. When it heats up, it will crack. I learned this the hard way after 2 quick failures.