Confused

I am making a beautiful pattern, but I am a bit confused as to how to sew the sides together. When I look at the picture, it looks to me like the sides are asymmetrical (which is what I want). However, the pattern only calls for rectangles sewn together. According to my thought process, to make the sides look asymmetrical, wouldn’t I have to make the inserts look more diamond shaped than rectangular?

I purchased the pattern from Ravelry- but really it is only 3 rectangles sewn together plus sleeves.

No one else has made the pattern (at least on Rav) so there’s no other info. I would just follow the pattern as it’s written. If it says it’s rectangles it probably is and just looks differently in the photos. I can see a rectangle on the side myself though.

Wait till you get to the sewing part and it will be easier to understand. It’s probably seamed with mattress stitch.