Cut 2 pieces of fabric into a rectangle, square or long rectangle for a neck heating pad. The two pieces should be the same size. Plan for a 1/2 inch seam allowance. That means you should add 1/2 inch to each measurement.
Place the 2 pieces of fabric with the same sides together. Line up the edges.
Sew a 1/4 inch seam around the outside of the rectangle, leaving a 1 1/2 inch opening for turning the pack right-side out.
Clip the the corners of fabric before turning it right side out.
Once the bag is turned right-side out, sew a seam on the right side about 1/4 inch in from the edge all the way around the bag, but leave the opening open.
Fill the heating pads with rice or your grain of choice. Use a funnel or index card rolled up to act as a funnel. Fill the fabric bag comfortably full, with approximately 1 cup of rice. Leave enough wiggle room to be able to sew the opening closed, but other than that, it’s a personal preference how full you fill the pack.