A neighbor, new to quilting, was over this morning as I was making the sashing for a wonky quilt. She asked why I was making the pieces as I was, and explained it was an easy way to make the little corner stones. I used to make the sashing the width of the quilt, but find I have much more control on lining the little corner stone up the way they need to be.
Sew the one strip on to one side, the right side in the picture. My block is 12-1/2" square and this strip is 2-1/2" x 12-1/2".
For the other side, I sew a piece of cornerstone fabric that is 2-1/2" wide by a length of fabric that is 12-1/2" wide. Press. Cut into pieces 2-1/2" long as you see at the bottom of the picture. Sew one of these pieces to the bottom of your block.
Then all I have to do is sew together the blocks and it's easy to do any adjusting is something was cut a smidgen off.
Hope this encourages anyone (like I used to be!) who is scared of getting cornerstones to look good. [II love the added dimension these little blocks make.