This makes a nice easy block. The square will be 11" unfinished. If you mneasure and find that your square is smaller then square all the blocks down by 1/2' or whatever the size of your smaller block. This won't hurt the block and you need not rip and resew any blocks.
If you have a hard time matching seams or rather not match seams when you sew the blocks together, sew in a small sashing between blocks. This is what I did. I did not want to match all those seams.