As everyone else has suggested your best bet is to graph it out. I would actually make those two narrow lines that jut to the left and towards the bottom a bit of the unit below and next. your upper right hand unit will need to be set in also known as a Y seam. Here, I modified your picture in paint with one option of how to break it into units drawn in red. Because you said you have already pieced the center nesting squares your options are limited in how to break this out. [ATTACH=CONFIG]543521[/ATTACH]