The Roll Player print and play game begs for upgrades. After purchasing and printing the card and player-mat files, upgrading seemed obvious. These Frame/Inserts work well with a foam core upgrade.
First, mount the player mats on Foamcore. I mounted one mat on each side of the foam core -- keeping the player race the same, just with male on one side, female on the other. Be careful to ensure that you mount the mats so that when you cut out the dice area, both sides align.
Then cut out the entire dice area, leaving the divider between the top nine dice and the bottom nine dice. If you were careful aligning the mats on both sides then the holes you cut will align nicely. Don't worry too much if your cuts aren't exactly perfect -- the flashing I built into the inserts will clean that up and make a nice clean line.
Then, put the left and right parts of the inserts in both the top and bottom dice sections. I used a small amount of crazy glue to keep the inserts in place. A friend also built this and said glue isn't really necessary.
Flip the mat over and repeat the insert/glue process.
Simple print with PLA. Make sure you print with the face down, so the flashing will not need supports etc.
Printed with Hatchbox Black PLA and AMAZ3D Copper PLA.
I built my Prusa MK3 partway through printing all these inserts, and the model prints nicely using the Prusa Slic3r application. Cura was my slicer for the Monoprice Mini Select.
Built it in Tinkercad. Originally started with a 3x3 grid but decided I wanted a different colour for the final 'gold' row. So broke up my 3x3 design into a 2x3 and 1x3.