This set uses one of my favourite techniques - hydro-dipping (or marbling).
With this technique, you drip special inks onto the surface of some water to make a pattern, then carefully dip a blank dice down into the water so that the ink folds around it. You then cast the patterned blank in resin to seal it.
I never would've thought of hydro-dipping dice, but it's brilliant and i imagine would be a lot of fun to do.
I really like the outer clear resin cast too, gives them another whole dimension.