If there is a lot of external fat on the pork loin, trim it to ¼-inch thickness. With a sharp knife, score the skin in a cross-hatched pattern, about 1/8-inch deep, avoiding cutting down into the meat (if the pork is tied, avoid the twine). Then make about a dozen ½-inch deep slits over the non-skin surface of the pork shoulder.
Season the pork all over with salt. In a food processor combine the fennel fronds, garlic, rosemary, sage, fennel seeds, lemon zest, pepper, red pepper flakes and olive oil. Pulse to combine thoroughly into a paste. Alternatively you can use a mortar and pestle.
Rub the paste all over the outside or the pork, pushing the mixture into the slits. If the pork has not been tied already, tie the pork with kitchen twine at 2-inch intervals creating a roundish, somewhat uniform shape. Place in a shallow baking large enough to hold the pork, cover with plastic wrap, and refrigerate from 6 to 24 hours.
Allow the pork to come to room temperature, which will take about 1 hour. Preheat the oven to 275F. Remove the plastic wrap and roast the pork loin for 2 hours, then pour the wine over the roast, and baste it (if you have time). Continue roasting and basting every hour (again, nothing bad will happen if you don’t baste), for another 3 to 4 or so hours until a thermometer inserted into the center of the roast registers 180 F.
Remove from the oven and let the pork rest for at least 15 minutes. Remove the twine, and slice the porchetta into thin or thick slices (your call!) and serve warm or at room temperature.
Notes
To crush fennel seeds you can use a mortar and pestle of a spice mill, or if you don’t have either, place them on a cutting board and use the handle end of a sturdy chef’s knife to crush them lightly on the board.