In a small bowl, combine salt, chili powder, cinnamon, and cloves. Pat the pork dry and generously season all over with the salt mixture. Cut a large piece (about 24 inches) of heavy-duty foil and place in a roasting pan. Add the roast, onion, garlic, and bay leaves and wrap everything up tightly in the foil. Roast for 3 1/2 hours.