I don't sew it in. I start out by cutting two pieces of plastic canvas the size of the bottom then I use a piece of yarn to tie them together in the corners. Then once I get the purse turned right sides out and have the lining in place, before closing the openeing that I turned through, I wiggle the canvas into the bottom of the purse through the turning hole. I then proceede to close the opening, and put the lining in place. I don't have to worry about sewing anything extra!