You start with the square of focus square and snowball the corners with a a bright fabric. You then use strips of the same bright fabric to make it a square again. Once it is square again, you snowball the corners with the black pieced unit to make it square again and then sew the squares together into a quilt top. The tricky part would be getting pieced corners exact so they match up when assembled. I might leave off piecing them and do them all one colour.