To make the adobo sauce combine vinegar, limejuice, chipotles, garlic, cumin, oregano, black pepper, salt and cloves in a blender or processor on high speed until smooth.
Remove most of the fat from the roast and then cut into large chunks (approximately 6). Pour oil into a frying pan and sear all sides of roast on medium-high heat until browned.
Place meat into Crockpot and pour adobo sauce over meat. Pour in the chicken broth and add bay leaves.
Cook on high heat 6 hours or on low all day.
While still in the Crockpot, shred the meat with two forks and turn the heat to warm. Serve with hard or soft tortilla shells when ready.