To make a baked potato bag, you will need a piece of cotton fabric, thread, a sewing machine, and insulation material. First, cut two rectangular pieces of cotton fabric according to the desired size of your bag. Place both pieces of fabric together with the right side facing each other and sew them together on three sides, leaving one end open. Turn the bag right side out and add the insulation material to the bag, leaving one inch of space from the top. Fold the top of the bag down by one inch and sew it shut, creating a hem. Finally, fold the bag in half with the opening facing up, and sew a seam down the two sides, creating a pocket for the potatoes to go in.