This tutorial for how to make a shoulder bag was submitted to Whip Up as part of their recycling/upcycling month.
It's made from a pillowcase which means that there is only one line of structural sewing.
It's really all about careful folding & cutting.
How To Make A Shoulder Bag From A PillowcaseView SlideShare presentation or Upload your own.
On Whipup here & there is a PDF how to available here.