Preheat the oven to 275ºF. In an 8-inch square baking dish, mix together the oil, orange zest, garlic, oregano, red pepper flakes, and 2 teaspoons salt. Add the pork and massage all over with the rub. 

Cover the dish tightly with aluminum foil and roast for 3 hours, flipping the pieces after 11/2 hours. Remove from the oven and let rest until cool enough to handle.

Preheat the broiler when ready to serve. Line a rimmed baking sheet with aluminum foil. Transfer the pork to a plate. Skim and reserve 3 tablespoons of fat from the baking dish. Shred each chunk of pork into a few thick pieces, spread the meat on the prepared baking sheet, drizzle with the reserved fat, and broil until the edges are crisped and lightly browned, 4 to 5 minutes. Season with salt and serve.