There are two types of abdominal belts. One type administers an electric stimulus to your abdominal muscles to cause them to contract and, in theory, build up the muscles' strength in the process. The second type of ab belt is designed to place additional pressure on the abs during a workout, thereby increasing the effectiveness of the workout in the same way that a hand placed on the abs makes sit-ups and crunches more effective. This type of ab belt can also cause the area to stay warm, which can help with weight loss and make ab workouts easier and yield faster results. You cannot make an electrical ab belt safely. But you can easily build the latter type and immediately use it to amp up your abdominal workouts safely and without potentially shocking yourself.
Determine the measurements for your ab belt. The belt should be 4 inches longer than the widest area around your abdominal area. The width should be twice the value, plus 1 inch, of the area of your body that you want to cover with the ab belt. Generally, your abdominal area is about 6 inches wide, so for the purposes of this example we'll assume that your piece of material for the belt will be 13 inches wide.
Cut out your material. Use even, smooth cuts so that the material is easy to sew. When you're done, you'll have a piece of material that is 13 inches wide and 4 inches longer than the length of the area around your midsection.
Place the cotton batting in the center of the strip of material. Cotton batting will add a bit of stiffness to the belt and also increase its warming potential. The batting should be rolled out down the center 6 inches of the belt, leaving 1 inch at either end of the belt and 3.5 inches on either side of the batting.
Encase the batting in the material. Fold the long edges of the material over the cotton batting. There will be about half an inch overlap of material. You will sew down this overlap using a zigzag stitch. Fold the inch at each end over the cotton batting and sew up the ends using the same zigzag stitch. You'll now have a long strip of stuffed material that is 2 inches longer than the length of the measurement of your abdominal area and 6 inches wide. It will have a line of stitching down the middle.
Stitch down the outside edges of the long portions of the belt. This will add stability and help prevent the batting from moving and wadding up inside the belt. You can use either a straight or zigzag stitch.
Attach the Velcro strips. One set of strips should be located at the ends of the belt so you can wear it on a loose setting. Match up the other sets farther in from the ends, so that you can tighten the belt to make your workout progressively harder as your abs get stronger.