I make them in squares to fit my lower back, sew channels in them, fill them 1/2 way with rice using a funnel and then sew the top side up. I attatch straps to the top of it so that I can tie it around my waist and hold it in place from my waist to where it rests on a chair. I make tubes to wear around my neck making them long enough that they will stay in place while I walk around. I have them without straps that I sit in my lap or on my lower legs and feet while watching tv. I place these in my bed if it is really chilly to warm it up before I crawl in.
I have some smaller ones I heat and put in my pockets to keep my hands warm when I go to get my mail, etc.... I also use these before I sew or type etc, to warm my hands before my stretching exercises.
I have even taken one of the big ones to the car on really cold mornings and have it inside my jacket or on my lap until my heater warms up LOL