For easy clean-up, place a cooking bag in your slow cooker. Coat the cooking bag (or slow cooker if not using a cooking bag) with cooking spray.
Cut the roast into large chunks and place in slow cooker.
In a bowl, mix together remaining ingredients and pour over the beef.
Cover and cook on low for 6 hours.
Remove beef from slow cooker and shred with 2 forks. Return shredded meat to slow cooker and stir. Continue cooking for 30 minutes.
Skim fat if needed before serving.