I saw a show about it sometime last year, either on Food Network, History, or Discovery. You take the raw skin, and blanch it in oil at about 300 degrees F for while (not sure how long). The skins will render out more oil in the process. After the blanching is done, you then deep-fry them in 450 degree oil (not sure about that, it may be hotter) until the skins crisp and bubble.
This is a vary labor-intensive process, not to mention that it produces huge quantities of fat as well as smoke. It's best done outside, or in a commercial kitchen with commercial exhaust hoods.
Where are you getting the pork skins from?
Peace, Love, and Vegetable Rights!
Eat Meat and Save the Plants!