Lay the pork belly, fat down, on a cutting board. Using a sharp knife, make a wide cross-hash pattern on the pork meat.
In a spice grinder, add the rosemary, 4 garlic cloves, fennel seed, salt and pepper. Grind until you have a thick paste. Add about 1/4 cup olive oil and mix further in the spice grinder to make a rub. You want enough rub to work into the knife slices of the pork so add more herbs and olive oil as needed.
Rub the mixture on to the prepared pork belly and work into the slices. Move to a sheet pan and cover tightly with plastic wrap.
Refrigerate at least overnight and up to 3 days.
When ready to prepare, remove the pork from the refrigerator and let warm up at room temperature for 1 hour. This will make it easier to roll.
Slice the fennel bulb into thin slices and place in a pot with a lid. Smash the 2 remaining garlic cloves and add to the pot. Fill with water to just cover the fennel. Bring to a boil and then reduce to simmer, cover and cook for about 15 minutes or until the fennel is very soft. Let cool.
Preheat the oven to 275ºF.
Fish out the fennel from the pot with your hands and squeeze most of the water out. Spread evenly over the pork. Discard the simmered garlic but retain the fennel water to use to baste the pork.
Now comes the part where you need a friend to help you roll up the pork belly and secure it. Depending on the length and width of the pork you have, you’ll need to figure out which edge makes the most sense to start with. Start with the shorter edge but if that’s too difficult to make a complete a complete roll, use the other edge.
Once you have a roll in your 2 hands, ask your assistant to tightly tie one edge with twine and then tightly wrap the whole roll with twine as shown in the picture. Secure the end with a final knot. Push any filling that fell out back into the center of the roll.
Place the roll seam side down in a glass baking dish. Drizzle extra virgin olive oil over the pork roll and rub all over the meat. Pour 1 cup of dry white Italian wine over the pork roll.
Slow roast in the oven, occasionally checking the center with a meat thermometer until the pork roll reaches 150ºF. The roasting pan will dry out during the roasting so check frequently and baste the roast with the fennel water and the accumulated juices.
When the roast reaches an internal temperature of 150ºF, crank the oven up to 500ºF. Carefully monitoring the roast, roast at this high heat until the outer fat is nicely browned. Carefully remove the oven and let cool to remove temperature.
Move the roast to a cutting board and snip off the twine with scissors.
At this point you can serve the roast immediately or place in a sealed container and cool in the refrigerator overnight. The taste will improve the next day.
Thinly slice and serve on crusty bread as a sandwich dressed with traditional Italian salsa verde.