I think it's basically 6" blocks (2.5" cut size centers framed with 2.5" cut size borders) and 12" strips with three 2.5" strips in each one. So make your blocks (they should end up 6.5") and then cut 12.5" strips and sew 3 together. Then sew each row up. The 6" blocks will go right in the middle of each 12" strip set. Cut strip sets shorter as needed for the end parts.