Here's my guess and how I would do it. They started off with a 6.5" square, cutting it (what I call a "snub") so that 2" would be left finished on the outer edges.
Then they took a 2.5" width and went around the snowball block for a 2" finished edge, just like you would a log cabin. It looks to me like the black was cut at 1.5, for a 1" finish and again went around.. Then they added the triangle. I always go large and trim down so I'd probably start with about a 2" square or something like that and just trim the whole unit nice and square.
You could build the triangles first but I think it would be fast as a log cabin technique.