Season pork belly all over with smoked paprika, salt, and black pepper. Wrap pork in parchment paper; wrap a second time in aluminum foil, and a third time in another sheet of aluminum foil. Place pork packet in a baking dish.
Roast in the preheated oven until tender for 6 hours. Let cool in wrappings to room temperature; place cooled packet in refrigerator and chill for 8 hours or overnight.
Unwrap chilled meat. Save any rendered fat that falls away when unwrapping pork.
Cut meat into 6 equal-size portions. Cut 1/8-inch by 1/8-inch slashes in the fat-side of the pork. Season with salt.
Heat 2 tablespoons reserved pork fat in a skillet over medium heat. Place pork belly, fat side down, in hot fat; cook until well-browned on all sides and heated through, 5 to 10 minutes. Transfer pork belly to a plate, drizzle with olive oil and season with pepper.