Add pork, water or chicken stock, and 1 tablespoon salt to a large dutch oven with a tight fitting lid. Liquid should just cover meat. Add additional as necessary. Place over medium-high heat and bring to a boil. Transfer to oven and cook, about 3 ½-4 hours, until meat is very tender and liquid is reduced to 1 cup. Baste meat every 45 minutes with cooking liquid.
Increase heat to 400 degrees F. Remove pot from oven and drain all but 3 tablespoons fat from pot. Add cumin, cloves, cayenne, and 2 teaspoons black pepper. Stir to combine, and return to oven. Roast, stirring after 10 minutes, until meat is browned, crisp, and liquid is evaporated, about 20 minutes more.
If meat is very fatty, you may need to continue to drain fat as pork crisps. Season to taste with salt and and pepper, and serve in tortillas, with cabbage, sour cream, pickled red onions, cilantro, avocado and serranos chiles.