Sparkly and square like a princess-cut diamond, but three-dimensional like a pillow: the all-new Princess Pillow Kit & Tutorial
The one in the picture (available here) features Jet 2XAB crystals, which are black fumed twice with gold. It gives them a blue, green, and yellow palette with orange holes (which you never see if they are just strung together).
It’s hard to tell from the picture, but it’s puffy in the middle like a piece of ravioli.
The tutorial includes a 1-inch-square pattern (shown here) and instructions for making it bigger and smaller using the same size crystals.