Set out a large 6-8 quart slow cooker. Preheat to high heat.
Cut the beef chuck roast into large 2 to 3-inch chunks and place them in the slow cooker. Then pour in the bottle of Bloody Mary mix, and add in the beef base.
Cover and slow cook on high for 5 to 7 hours. Or cook on low for 10 to 12 hours.
Once the beef is fork-tender, use two forks to shred the beef into the juices. Remove any large chunks of fat if desired. Set the slow cooker on warm until ready to use.
Notes
Pro Tip: Look for “good” Bloody Mary mix with tons of spices and little to no filler or preservative ingredients.Cool completely and store in the refrigerator for up to 5-6 days in an airtight container. The shredded beef will keep well for up to 3 months in the freezer.