Even in this day and age not everyone has a microwave. In fact, natural heating pads were being used long before microwaves were even invented. In times past, natural heating pads were warmed by the hearth or oven. here is an easy way to do it yourself.
*Heat oven to 350 degrees and then turn it OFF.
*Place heat pad in a baking pan or cookie sheet and spread it out flat.
*Place in turned off oven for about 30 minutes.
You can experiment a little with the time to get it just right, but be sure to always have the oven off before you put the heat pad in.
If the pan you are using has baked on grease, you can place a paper towel under the heat pad to protect it from oil stains.
If the oven is used for cooking supper, once its turned off you can use that residual heat to warm your heat pads for your family to use as bed warmers. In the winter time, this is a ritual that kids just love!