Templates hold one or multiple of the same product squared and steady. If you are lasering multiple products in the same batch, exact placement on your table is critical. My main substrates for templates, especially ones I use infrequently or only once, are sheet acrylic (especially scrap), cardboard, and paper. I save all the cardboard from the back of writing pads. I find some in packing from suppliers and many other places. Many of my templates are used to hold keyrings, round inserts, pen knives, bottle openers, and many other small gift items or promotional products.
The setup I use to laser cut my product templates becomes my graphic software template for placing the text and graphics to be lasered. I just make sure this digital template is put on a software layer that is not printable and not visible.
If cardboard or 1/16″ sheet acrylic is too thin to hold the product securely in place, consider doubling the material or adding thin strips of the material around the bottom outer edges of the template.