So I was looking at this X-block ruler and the pattern that was with it (it was in the estate sale box...), reading how it works. I realized that I had some coordinated fabric with the exact amount of yardage that the Topsy Twosy pattern required.
These fabrics are from Heidi Grace's Only Time line of fabrics. There were bolts in the red dot clearance section at JoAnn's during a half off sale. I paid $1.50 a yard! I knew I would use them eventually...
So I followed the cutting instructions exactly:
...then started sewing the strips together.
The strips get cut into pieces and sewn into blocks (left side of pic). Position the X-Block template according to the lines and cut. (See the extra right triangles at the top? They will make a second quilt, included in the instructions! No waste, hip hip.) The smaller block on the right is one-fourth of the finished block.
Here are four units put together to make one large 12.5" X 12.5" block.