Place roast in the slow cooker and pour water, beef broth, and soy sauce on top. Sprinkle with the spices, toss in the bay leaf, and cover.
Cook on low for 6 hours. Remove from slow cooker, slice, and place back in broth and cook on low 30 more minutes.
Place meat on a platter and strain all the broth into a bowl to serve with sandwiches.
Cut the buns in half. Spread butter on the inside of each half and place on a baking sheet. Broil of 1-2 minutes until lightly toasted. Turn oven to 350. Set the top buns aside, leaving the bottoms on the pan. Place meat on buns and top with cheese. Place in oven for 3-5 minutes until cheese begins to melt. Remove from oven, close bun, cute sandwich in half, and serve with au jus.