Design the mould · 3D-print it · cast your mat
Design a silicone mat full of holes for your UV printer - no CAD needed. What you download and 3D-print is the mould; you pour silicone into it to make the mat itself. Pick your printer's bed (or a custom size), choose how big the holes are and how far apart, round off the corners, add an optional alignment grid, and split the design into interlocking pieces if your 3D printer is too small to do it in one go. There are printable jigs too - they plug into the mat's holes to hold your parts still while you print on them.