(Note - I reversed the order of the stack from the picture above before I started this next step.) Take the first row (green), and set aside one block. That will be your upper right corner. Take your second row (pink), and chain stitch together one block from each row. When you're done, you'll have one leftover block from row 2.
Take one of your 1+2 combos (green+pink), and set it aside. Take that extra row 2 block (pink) and put it under your pile of 1+2 combos. Pull out row 3 (blue), and proceed to chain stitch one blue block onto each pink block.
Now you have sets of 3 (green+pink+blue), plus one set of 2 (pink+blue), plus one leftover blue. Put aside one set of 3, and put the set of 2 and the single under your stack of 3's. Grab the next row, lather, rinse, repeat!! Keep pulling one off the top, and putting the new single one on the bottom, and soon enough you'll be all done. Yay!
Here are the rows laid out on my "design floor". :-)
I was going through my stash of sheets, and this one caught my eye. I think it will be perfect for the back of this quilt.
Just for fun, here's a shot of my sheet stash. That's all pillowcases and small cuts on the top, and whole sheets on the bottom. Whee!