Trim and square off the pork belly to fit in your pan.

Place pork belly skin-side down on a large cutting board. Using a sharp chef's knife, score flesh at an angle using strokes about 1-inch apart. Rotate knife 90 degrees and repeat to create a diamond pattern in the flesh.

Toast peppercorns and fennel seed in a small skillet over medium-high heat until lightly browned and aromatic, about 2 minutes. Transfer to a mortar and pestle or spice grinder and grind until roughly crushed. Mix in 2 tablespoons salt, red pepper, minced herbs and garlic to form a dry rub.

Season pork liberally with the salt/herb/garlic mixture . Use your hands to rub the mixture deeply into the cracks and crevices in the meat.

Roll pork belly into a tight log and push to top of cutting board, seam-side down. Cut 12 to 18 lengths of kitchen twine long enough to tie around the pork and lay them down in regular intervals along your cutting board, about 1-inch apart each. Lay rolled pork seam-side down on top of strings. Working from the outermost strings towards the center, tie up roast tightly. Combine 1 tablespoons kosher salt with 1 teaspoon baking powder. Rub mixture over entire surface of pork roast.

If roast is too large and unwieldy, carefully slice in half with a sharp chef's knife. Wrap tightly in plastic and refrigerate at least overnight and up to three days. If desired, porchetta can also be frozen at this point for future use.

Adjust an oven rack to the lower-middle position and preheat oven to 300°F. Place pork in a v-rack set in a large roasting pan, or if cooking both halves at the same time, on a wire rack set in a rimmed baking sheet. Place roasting pan in oven and roast until internal temperature of pork reaches 160°F, about two - three hours, basting with pan drippings every half hour. Continue roasting another two hours, until a knife or skewer inserted into the pork shows very little resistance asides from the outer layer of skin. Better to roast long and slow to ensure the fat melts under the skin. The temperature will reach up to 200 degrees and still be delicious.

Remove pan from oven, and set roast aside. Carefully pour off the hot oil into an old coffee can or similar vessel. Let oil cool, and toss, or strain and save all the bacon fat for other recipes.

Increase oven temperature to 500°F. Return roast to v-rack, and continue roasting until completely crisp and blistered, about 20 to 30 minutes longer. Watch closely so it does not burn. Rotate the roast to be sure the underside crisps as well if necessary.

Total cooking time will be close to 5 hours or more, depending on the size of the roast. Alternatively, you can remove the roast from the oven and tent with foil for up to two hours before finishing it in a preheated 500°F oven.

Tent with foil and allow to rest for 20 -30 minutes. Slice with a serrated knife into 1-inch thick disks and serve.