Put roast beef into slow cooker and season with Kosher salt and pepper on all sides.
In a small bowl, mix together all remaining ingredients. Pour over roast beef.
Slow cook on LOW for about 8 hours, or until meat easily shreds apart.
Using two large forks, shred the meat apart in the slow cooker.
Serve meat warm on top of mashed potatoes or polenta. Alternatively, serve on a bun or ciabatta roll with sauce on the side for dipping.
