Spray slow cooker with nonstick spray, add chuck roast, mix au jus, gravy, and water, cover, and cook on low for 8-10 hours.
Remove tender beef from slow cooker, shred, discard fat, and add to gravy. Preheat oven to 400°F and warm bread for crisping.
Dress bread with mayo, Creole, mustard, beef, gravy, cabbage, pickles.