I've done a ton of dice over the years. The best way I've found is simply to laser cut a registration grid that has a square hole (maybe half a millimeter larger than the dice) for each die that is maybe 1/3 of the dice size deep. Make sure this registration grid is firmly secured to your bed so it doesn't shift or move. Then load it with the blank dice and engrave one side on each die across the entire grid. Then you move the laser head out of the way and rotate each dice in a predetermined direction and engrave the next side. Rinse and repeat until all six sides are engraved. Your master laser file will have the same grid that you simply copy/paste with the different numbers or images you want on each dice side. Make sure to cut your registration grid right before you do all your engraving so it stays in perfect registration with your graphic engraving you do on the dice. Your registration grid can be anything cheap like a couple stacked layers of cardboard that are taped securely to your laser bed. Laser cut the registration grid, then pull out the cardboard squares and you have a perfect, cheap dice registration grid.