Add the fennel seeds to a dry skillet and toast until fragrant over medium heat, around 2 minutes. Transfer to a mortar and pestle or spice grinder and grind to a fine powder. Set aside.
Place the pork meat side-down and, using a very sharp knife, lightly score the skin in a cross-hatch pattern. Then, flip the pork so that it’s skin side-down and score the meat in a cross-hatch pattern, slicing around one quarter of an inch deep.
Keeping the pork skin side-down, liberally season the meat with salt and pepper, then evenly distribute the ground fennel, chili flakes, garlic, sage, rosemary, thyme, orange zest and lemon zest. Using your hands, massage the seasonings into the crevices of the score marks.
Tightly roll the pork so that it’s seam side-down and skin side-out and tie with butcher’s twine. Be sure to trim off any outer skin that overlaps as you roll the pork into a log. Skin that is not exposed to hot air will not dry out or get crispy.
Line a sheet pan with a wire rack and place the pork on top, seam side-down. Season the skin with salt and refrigerate, uncovered, overnight or up to 48 hours.
When ready to cook, preheat your oven or Traeger Grill to 350F. Transfer the wire rack and pork onto a 4”-deep roasting pan. Place in the lower half of the oven, or middle of the Traeger, and pour 2 cups of water into the roasting pan. Cook until the internal temperature of the thickest part of the meat reaches 160F, around 3 hours. If the water evaporates during the cooking process, add more.
Remove the porchetta, tent it with foil, and increase the heat of the oven or Traeger to 500F. Pour the rendered fat into a sauce pan and place it over medium-high heat until it reaches 375F. Baste the porchetta with the hot fat and return it to the oven until the skin is blistered and crispy, around 25 minutes.
Transfer the porchetta to a carving board, tent it with foil and let it rest 30 minutes before carving into 1/8-inch slices with a very sharp knife. Serve with condiments of choice, such as the Classic Salsa Verde from The Primal Gourmet Cookbook.