Very simple, just a ruler to number your slats, so on repetitive tasks where you might clash with clamps, you can note where to put your slats. (Ignore the wolves!) It is 590mm long so easy to cut from a 600mm sheet, missing out slat 1, 46 and 47 (You can figure slat one and you don't tend to use the last two slat positions)
Cut it from a scrap piece of ply. It can stay in your machine as it is out of reach of the laser head it you but it right at the bottom