Carrying Bag Made From a T-shirt, With Special "flat" Bottom Design

After I uploaded my first Instructable how to make a grocery bag from a t-shirt, I discovered a flaw in the design.  I thought sewing the corners in a diagonal seam would allow the bag to have a flat bottom, but it doesn't.  So with the help of some good friends I now present the CORRECT way to make a "flat bottom" grocery bag.  With its own carrying sack.

Older and simpler Instructable here:
https://www.instructables.com/id/Easy-to-make-grocery-bag-made-from-a-T-Shirt-W/