Thank you. I made it up! Place one coloured 4 1/2" strip onto one background 4 1/2" strip ( both strips need to be right side up) . Cut 4 1/2" rectangles. Make slightly slanted cut through both layers from the bottom to the top and approximately in the middle of each pair of rectangles. Swap the pieces and sew them together to yield two two-tone units. I'm sure this would work with any size squares, depends how big you want them.