The Falcon 2 Pro laser cutter by Creality comes with a platform consistion of slats. These jigse are registered to the bed at either 90 or 45 degrees for repeatable positioning of material. The height is below the Z axis position of the laser for 3mm material.  

I got the idea from:     https://www.printables.com/model/1128793-creality-falcon2-pro-anti-rattle-slat-brace-tpu