Add all of the ingredients to the slow cooker and toss to combine.
Cover and cook on low for 6-8 hours, or on high for 3-4 hours, or until the beef is tender.
When the beef is tender remove it from the liquid and and place it in a bowl. Shred the beef with two forks into bite sized pieces.
Remove the bay leaves and then spoon the liquid from the slow cooker on top of the shredded beef. Allow the beef to rest for 10-15 minutes. This allows the beef to soak up some of the liquid.
Season with salt and pepper to taste and serve immediately in taco shells or bowls or over rice.