The night before you’re ready to serve, score the fat of the pork about a ¼ inch deep. Mix salt, pepper, garlic and onion powder, and cumin, and thoroughly rub into the pork, being sure to get the mixture into the crevices of your score. Wrap well in plastic wrap and leave in the fridge overnight.
The next day, unwrap the pork and place on paper towels, drying the meat, and gently brushing off any excess salt. Preheat your oven to 375 degrees and put a large pan with vegetable oil over high heat. Once the oil is very hot, sear both sides of your pork, fat side down first, until golden brown. Set aside. With the heat still high, immediately saute your fennel, onion, and garlic with the rendered pork fat until they just begin to brown. About 5 to 10 minutes. Place in a high sided baking sheet and place your pork on top, fat side up. Finally, add wine to deglaze the pan and simmer for about 5 minutes. Pour over the pork and fennel mixture. If needed, add water to the baking sheet in order for the amount of liquid to just reach underneath the fat line of the pork. Do not fully submerge. Cover with foil and roast for 2 hours. After the pork is cooked, remove from the pan, and set aside on a separate baking sheet. Keep in the fridge until ready to serve.
Using a slotted spoon, put fennel, onion, and garlic in a blender. With a fat separator, separate the liquid from the pork fat. Add the liquid to the blender. While blending on high, slowly drizzle in the pork fat to emulsify to make gravy.
When ready to serve the pork belly, cut appropriately into individual serving sizes and quickly roast in the oven, uncovered, at 375 degrees for 15 minutes until the fat becomes golden.