It will be a few days before I can get a pic of the back. It belongs to my friend Cathy and it resides in her home. But I will get one for you to see.
The way I understood it: joining the squares together will create the straight lines on on the back, then the curved lines will be seen on the back as you add each "window".
Hand stitching this took Cathy's Mother 3 years with other projects during this same time.