The basic instructions are: turn the t-shirt inside-out and sew the bottom shut. Turn right side-out and lay flat. Use a large bowl to trace a half circle at the neck then cut. Finally, cut off the sleeves and your bag is done.
I love these bags. These particular t-shirts were quite stretchy so they aren't great for carrying heavy things but they are perfect for taking a towel and a book to the beach or getting a few veggies from the store. They scrunch up into a pretty small ball so it's easy to just toss one in your purse. I might end up making all my old t-shirts into bags!