Pat the pork belly dry, with paper towels. Use a Jaccard or fork to poke holes all over the pork belly skin. Sprinkle the skin of the pork belly with Kosher salt or sea salt and place, skin side up and uncovered, in the refrigerator overnight.
Use a knife to butterfly or "unroll" the pork loin so it is about an inch thick.
Combine the chopped herbs, garlic, ginger, 1 teaspoon of salt, and lemon juice and mash and mix to form a paste.
Combine the fennel and peppercorns in a bowl or mortar and pestle and crush the spices until a coarse spice mix is formed.
Evenly cover one side of the butterflied pork loin with the herb paste, followed by the spice mix.
Roll the pork loin back up, so that the seasoning is on the outside of the pork. Place the pork belly, skin side down and place the seasoned pork loin in the center. Roll the pork belly up, around the pork loin.
Truss the porchetta with butcher's twine, at 1-inch intervals, to keep the pork belly wrapped around the pork loin.
Cooking the Porchetta
Prepare your grill with rotisserie and preheat to 325 degrees.
Place the porchetta on the rotisserie skewer. Cook at 325 degrees for about 2-3 hours, or until the internal temperature of the pork reaches 140 degrees.
Increase the temperature to above 400 degrees and cook for about 5-15 minutes until the skin has fully crisped up.
Remove the porchetta from the rotisserie and let it rest for at least 10 minutes on a cutting board before slicing.