Combine garlic, salt, and pepper; rub entire surface of roast with mixture. Place in a large container
Combine water, vinegar, onion, sugar, peppercorns, and bay leaves in a large saucepan. Cook over medium heat 5 minutes. Pour sauce over meat; cover and refrigerate at least 7 days, turning meat once a day.
Remove roast, reserving marinade. Remove and discard peppercorns and bay leaves from marinade. Dredge roast in flour. Brown roast on all sides in hot oil in a large Dutch oven. Add reserved marinade; bring to a boil. Reduce heat; cover and simmer 3 hours or until roast is tender. Remove roast to a serving platter.