I just finished making 7 of these out of shirts. They finished at 50x60...I cut 6 inch blocks(so that I could use a 6 " sq ruler)
and simply sewed them together in a diagonal pattern. I used the layer and turn method, pressed the edges, and did a topstitch 1/2" from the edge, then quilted them on my Gammill, no bonding! I used a pocket from 7 of the shirts to make the labels.