- 1 pork belly, skin on, about 10 to 12 pounds
- 1/2 cup kosher salt
- 3 tablespoons baking soda
- 5 medium garlic cloves, sliced thin, preferably using a mandoline slicer
- 2 sprigs fresh rosemary, leaves removed and chopped
- 3 tablespoons fennel seed, coarsely ground in a mortar or electric spice mill
- Season the meat side of the pork belly liberally with the salt. Flip the pork belly over and rub the baking soda evenly into the skin.
- Leave the belly in the fridge overnight with the skin side facing up, uncovered (if you have trouble fitting the pork belly into your fridge, you can cut it in half).
- The next day, heat the oven to 400°F. Arrange one rack in the upper third of the oven and another in the lower third. Remove the pork belly from the fridge and lightly pat the skin with a paper towel to dry it.
- With a razor blade, carefully score the skin to expose the fat, without piercing it. Score in diagonal lines 2 inches apart. Then score in the opposite direction, also 2 inches apart, to create an even diamond pattern in the skin.
- Flip the belly over so the skin side is down. Evenly scatter the garlic slices over the meat. Follow with the chopped rosemary, coarsely ground fennel seed, and lemon zest.
- Roll up the belly and, with butcher’s twine, tie it together at 3-inch intervals. Make sure the twine is snug but not too tight. In order to fit the pork belly in a standard oven, you’ll need to cut it in half to make 2 roasts.
- Place the roasts on a pair of wire racks set inside 2 rimmed baking sheets. Roast for 40 minutes.
- Reduce the oven temperature to 325°F and roast undisturbed for 3 hours, or until the interior of the porchettas is tender. Use a long wooden skewer or long, thin knife to probe the meat to determine its tenderness—it should be very pliant but not falling apart.
- Raise the oven temperature to 500°F and roast until the skin is evenly blistered and crispy, about 20 to 30 minutes.
- Remove the porchettas and let them cool for 30 minutes. Slice as thick as you like—if you’re making sandwiches, 1 1/2 inches is about right—and serve.