Pour water into slow cooker, and set the cooker to High to preheat. Heat the vegetable oil in a large skillet over medium heat, and brown the pork on all sides, stirring occasionally, about 10 minutes. Place the browned pork into the hot water in the slow cooker, leaving oil in the skillet. Cook and stir the green and red bell peppers, onion, and garlic in the hot skillet over medium-low heat until the onion is translucent, about 5 minutes. Transfer the vegetables into the slow cooker. Drop in the bouillon cubes. Add water if necessary to barely cover the ingredients, set the cooker to Medium, and cook until the vegetables are tender, 1 1/2 to 2 hours.
Pour in the diced tomatoes with chiles, and stir to combine. Cook for 1 more hour; stir in the hominy with liquid, cumin, red pepper, and black pepper, and cook 1 additional hour.