Score the fatty side of the pork belly with a knife, about ¼" deep in a crosshatch pattern 1" apart.
Rub 1 tbs kosher salt onto the fat and turn over. Rub 1 tbs of kosher salt on the other side. Place in a non-reactive pan (like glass), cover with plastic wrap (NOT FOIL) and refrigerate overnight.
The next day, preheat the oven to 325°. Remove the pork belly from the refrigerator and allow to warm up a bit. Grind the garlic, annotto paste, oregano and lime juice in a molcajete or food processor. Add more lime juice as necessary to form a paste. Place the pork belly in a large pan, preferably on a roasting rack. Rub the paste onto both side of the pork belly.
Position the pork belly fat side up. Add minced onion, peppers to the pan, partially on top of the pork belly. Sprinkle cumin and black pepper over the pork belly. Cover with a piece of parchment paper or cover the pan with aluminum foil. IMPORTANT: Do not let the foil come in contact with the pork belly. The salt will corrode the aluminum and make a mess on the pork belly. Cook for 4 hours. Allow to cool, then wrap in plastic wrap and refrigerate overnight.
The next day, slice ¼" strips from the pork belly and cut each strip in half.
Pan fry the cut strips in a fry pan with olive oil until slightly crispy (about 10 minutes). Turn three times.
Heat canola oil in a large pot to 350°. Cook thin yellow corn tortillas in the hot oil (using taco tongs) until done (about 30-45 seconds).
Load crisp pork belly into the shells, sprinkle with cilantro and add your favorite toppings. Enjoy!