Cut small slits in the pork roast with a sharp paring knife and place a silver of garlic in each slit. Sprinkle the pork roast generously with salt and pepper. Combine the pork, water, soy sauce, vinegar, brown sugar, and cumin in a large pot or Dutch oven. Bring to a boil, reduce the heat to medium-low, and simmer, covered, turning the pork occasionally, until fork tender, 1-1/2 to 2 hours.