I’ve just finished https://www.etsy.com/uk/listing/1337391189/retro-tec-sling-bag-sewing-pattern?  for my DD.

It’s the first Kandou Crafts pattern I’ve made and I’m quite pleased with it.

My only niggle is the internal binding. I’ve always birthed a bag so the seams are enclosed but this one has the seams bound with bias tape after assembly.

I found it really difficult to keep the binding neat with all the lumps and bumps of the seams. The designer suggests trapping the seams within the binding and sewing with one pass but I couldn’t get a decent finish this way, so resorted to hand sewing the backside of the binding.  [ You are not allowed to view attachments ]    [ You are not allowed to view attachments ]  

I learned to sew on an older model of this, and still use it in my alteration shop.  Great machine!

I'd stick with squares, rectangles or strips as there aren't any triangles in it already. A border top and bottom of 5" squares perhaps?
How big are the existing blocks?

Your colours are glorious @Bjay.