Usually, cathedral window quilts are made with the colorful parts in the sort-of-square shapes (with bowed in sides), and the other parts are a plain type of background fabric (often white or off white). You layout diagram shows the
reverse. Is that
really what you want???
Assuming you want the traditional placement of the color, I suggest checking out Angela's Walters
video - she clearly shows how to plan the layout and sew the squares together.