I cut a lot of 3 mm plywood in my Gweike LC1390N laser cutter and most often the plywood is warped. With a couple of these things, I can flatten the material. However, sometimes the sheet is so warped, that it lifts the knifes, but that's easlily adressed with some weights on the knife. STEP-file is also added, so you can tinker with it and adapt to your own knife and material thickness.

PLEASE - dont copy and sell this on Etsy or whatever.... I can sell you a commercial license for it.