I made a couple of these and they are fabulous! Never have to buy expensive heating pads again. Help those sore muscles with these homemade packs. In Asian this idea is very common. I saw reminded of this when I saw it on pinterest. Great to use up your fabric scraps. Just sew a square or rectangle. I added the flannel fabric to help it retain heat better. I also added adjustable elastic straps to the pack. This will keep the pack in place more. I need mine to stay around my belly after having a baby. Before you sew the piece together pin the elastic bands on the Right side of the fabric. Right sides together zig zag stitch. I used my overcast foot which gives the same effect as a serger. Happy to save money not having to buy a serger. Just get the sewing foot. I further reinforce it with a straight stitch about 1/4 inch seam allowance. Give yourself an opening probably best to do this after you sew in the elastic band first this makes it for you to turn your project. Turn it right side out and fill the rectangle half way with rice. Then tuck in the raw edges and sew close the opening. There you have yourself a heat pack! Pop it in the microwave for a 1 minute for smaller 4x4 or 2 minutes for larger size. Depending on your microwave strength you can fiddle with it till you get it so it doesn't burn your skin. Be warn it can get really hot! Make more smaller version without the straps to freeze and put in your lunch box and go on a picnic.