I’ve been engraving a ton of cutting boards lately that are too thick for use on top of the crumb tray. Normally, I use 3D printed risers from Thingiverse to get the boards propped up into the laser zone. This requires finding the center of each board, running a low powered score, and making adjustments to ensure it’s centered. I designed and built this crumb tray replacement jig to make repeat jobs faster and always centered. The boards I’ve been using are about .675" thick. The risers are 1.097" from the floor of the Glowforge, so cutting boards between 0.406" and 0.877" thick should work on this jig. The risers could be modified to accommodate thicker materials, but this works for the boards I’ve been using from Ikea.
If this could help you, here is the link.