The die pictured in the main image was printed in Hatchbox silver PLA. Recommended layer height is 0.1mm or less - the steep overhangs of the bottom faces strongly benefit from the thinner layers. Also, I would highly recommend using Prusa Slic3r for this. There are two reasons for this: 1. The "Ensure vertical shell thickness" option helps a lot with the angled surfaces. 2. The Cubic infill option seems to be very well-balanced and does an admirable job of making this part very strong. Also, for fairness, be sure that your top and bottom surface thickness is the same. In other words, make sure your top and bottom layers settings are equal unless you're using a thicker first layer, in which case that thickness difference needs to be subtracted from your bottom layers. Conversely, you could also load this die pretty toward either 6 or 1 easily by adding more solid top or bottom layers, which is why making it fair takes a bit of care. If you're going to do that, though, at least be honest with your fellow players. Some DMs/GMs might even let your character get away with it if they're a particularly lucky character, but at least be honest about it.