Make the Spice Rub

Cup of Yum
1. Combine fennel seeds and peppercorns in a small skillet. Toast over medium heat, stirring often, until lightly golden and fragrant, about 3-5 minutes. Cool and transfer to a spice grinder. Pulse until finely ground. (Alternatively, you can use a mortar and pestle.)
2. In a small bowl, combine the ground spices with sage, rosemary, thyme, lemon zest, orange zest, garlic, and red pepper flakes.

Assemble the Porchetta

1. Use the tip of a paring knife to make small holes all over the meat side of the pork belly. Season with about 1-1/2 teaspoons kosher salt and and half of the spice mixture, rubbing it into the meat.
2. Season the pork loin with 1-1/2 teaspoons of kosher salt and the remaining half of the spice mixture. Tightly roll the pork loin from the long end into a cylinder.
3. Roll the pork belly (skin side out) around the rolled pork loin. Tie the loin with butcher's twine at 1-inch intervals. 
4. In a small bowl, combine 1 tablespoon kosher salt and 1 teaspoon baking soda. Rub the salt and baking soda mixture all over the skin. 
5. Place the porchetta on a rack set in a roasting pan or rimmed baking sheet. Refrigerate, uncovered, 24-48 hours.

Roast the Porchetta

1. Take the porchetta out of the refrigerator 2 hours before roasting and allow to rest at room temperature. Preheat oven to 275 degrees F.
2. Roast the porchetta for 3 to 3-1/2 hours, until the internal temperature of the pork loin is 140 degrees F. Remove from oven, tent with foil, and increase oven temperature to 500 degrees F.
3. Uncover the porchetta and return it to the oven to roast until the skin is deep golden and crispy, about 15-20 minutes longer. Watch it closely so it doesn't burn.
4. Place the porchetta on a carving board, snip and remove the twine, and let rest 10 minuets before slicing. It can be helpful to use a serrated knife to cut through the pork skin. If desired, cut the skin (crackling) into small pieces to serve alongside the sliced pork. Serve hot.