Cut the pork belly into 1/2 inch slices. Heat a large skillet over medium heat and add the pork belly slices. Cook for about 5 minutes, flipping the pieces occasionally until they are lightly browned.
In a small bowl, combine the sugar, fish sauce, soy sauce, garlic and pepper. Pour the mixture over the pork belly and cook for an additional 10 minutes, stirring often.
When the pork belly is cooked through and tender, remove it from the pan to a plate and let it cool before wrapping in lettuce leaves or rice paper wraps.