Roll the pork belly up, lengthwise, into a roll and mark the section of skin that ends up covered by the meat. Trim this section of skin off.

Thoroughly rub the entire belly with olive oil. Generously season the meat side of the belly with salt and pepper. Evenly spread the chopped garlic over the meat, followed by plenty of fresh rosemary and fennel fronds.

Roll the porchetta up again and tightly tie it shut with several wraps of kitchen twine. Refrigerate the porchetta, uncovered, overnight.

Preheat an oven to 300°F (150°C). If you have a large capacity air fryer that can comfortably fit the porchetta with a few inches free from the heating element, preheat it to 250°F (120°C). Roast the porchetta until it reaches an internal temperature of 165°F (74°C). While it’s important to cook by temperature, not by time, our 2.5 pound pork belly roasted in about 90 minutes, for reference. A larger porchetta can take significantly longer, as much as 3 hours.

Remove the porchetta from the oven. If using a conventional oven, preheat the broiler to the maximum temperature and set up a high rack close to the heating element. If using an air fryer, preheat it to 380°F (195°C).

Pierce the pork skin all over with the point of a sharp paring knife. Cook the porchetta, turning it frequently to cook all the sides evenly, until the skin is bubbly and crunchy. Depending on your oven, this process can be fast so keep a close eye on the porchetta.

Let the porchetta rest for 10 minutes before removing the twine, slicing and serving.