Preheat oven to 500f and move rack to lower third. Dry off pork belly skin and trim the belly and loin to fit together for one complete roll. Mince 8 cloves of garlic, zest 2 oranges and chop the parsley and rosemary. Toast the fennel seeds and pignoli nuts in a pan on medium-low heat for 5-10 minutes being careful not to burn. When toasted set aside.
In a clean pan saute garlic in a 1/4 cup of olive oil on medium heat for 2-3 minutes. Add the breadcrumbs, chili flakes, herbs, pignoli nuts, fennel seeds and the juice of 2 oranges. Mix well to form a paste. Set aside.
Score dry pork belly in crisscross pattern on skin side. On other side score 1/4" deep lines into the pork. Season the non skin side with 2 tsp of kosher salt. Next place stuffing mixture onto meat and evenly distribute it by pressing it into the meat. Sprinkle all of the orange zest on top.
Season pork loin with 1 tsp of kosher salt and place on one side of belly to start rolling. Roll the porchetta tightly and tie off every 1" or so to make a uniform cylinder.
Dry the porchetta one last time with paper towels, then season with 2 Tbsp of kosher salt. Rub it into the skin all over. Place the porchetta on a wire rack inside a roasting pan. Inside the roasting pan pour 1 cup of water making sure that the liquid does not touch the roast.
Roast the porchetta in the oven for 45 minutes on 500f turning once at halfway point. After 45 minutes turn heat down to 300f and continue cooking until 145-150f internal temperature is reached. Make sure to rotate the roast every 30 minutes to achieve even cooking. For an 8 pound roast it should take 2.5-3 hours more.
When finished remove from oven and let rest for 20-30 minutes before serving. Remove twine, slice and enjoy!
Try to use skin on pork belly - the dish is still excellent without.
Make sure to salt the belly on both sides and the loin.
To get a perfect cook check internal temperature with an instant read thermometer every so often.