I sew mine before cutting off the block just as Margecam52 reply #6 and w7sue reply #38 do. Fabric is too expensive to throw away. I have been given sacks full of tiny and larger triangles by LQS's. They don't take the time to sew them together so I have to do that. It is surprising how many blocks or quilts one can make from the LQS's leftovers or my own. The end result is equally as useful a quilt as one that you purchase all the fabric to coordinate.