I have 6 x 9 x 3/32" glass and used a thick layer of hair-spray to attach it directly to aluminum plate, on CTC printer.
Used clips to hold it in place while drying, took about 12 hours for hairspray to dry completely, under the glass.

It has Stayed in place very well, knocking and prizing objects off glass has Not moved the glass.

Note: I also use hair-spray to hold printed objects on glass