I think it largely depends on the texture they’re trying to achieve; those puffy ones you linked will definitely be twice fried/baked and fried.
The recipe I found actually uses Avocado oil, but you can of course always just fry them in the rendered pig fat from the initial bake, or just add lard ; )
I’m not seeing just pig skin as an option to buy anywhere near me but when I make my next Field and Flower order I’m planning on getting a good whack of pork belly, so may just trim the skin off that and give it a whirl : )