First, cut your fabric to 8" x 24". Fold it lengthwise with the good side of the fabric on the inside. With a 1/4" seam, sew around two sides and leave one side open.
Turn the fabric tube right side out and fill with approximately, 6 cups of white rice (not instant). You don't want to fill it completely full because then you won't be able to bend it.
Once, it is filled with rice, take the open end and fold it in about 1/2".
Then sew it shut.
Now you are ready to soothe all of your aches and pains!
You can either pop it in the microwave for a minute for heat or toss it in the freezer if you need to cool down.