You could do it with strips ...looks like 5 strips -a white strip, a blue strip, then a middle print strip, then a red strip and then another white strip. to come out 12 1/2 inch.block.. make white, blue, and red strips 2 1/2" wide and the middle print strip 4 1/2" wide. I will make up a sample block and see if this works and try to post it!
You could draw up paper templete for pp piecing or use the freezer paper method. in the size block you want..
bias seams ..starch helps and careful not to stretch the seams! pp piecing helps ...
Hope this helps ...