Cordelia, they are just log cabin blocks on point. The big ones are made up of a small black square, then a 2" log cabin around that, and another colour 2" log cabin piece around that one.
The small ones are made the same way, but the outside piece is the same black as the background, so it looks like they are "floating". Then they are placed alternately on point, so colour outside, black outside, like that, in rows. Does that make sense?
Nancy Jean