Place the beef chuck roast in the slow cooker. Sprinkle the dry onion soup mix, au jus gravy mix, garlic powder, onion powder, and black pepper over the roast.
Add beef broth, French onion soup, Worcestershire sauce, and soy sauce, ensuring the beef is submerged. Cover and cook on Low for 7-8 hours or High for 4-5 hours.
Let the roast cook until fork-tender, easily shredding with two forks.
Transfer the beef to a cutting board and shred it with two forks. Return the shredded beef to the slow cooker to soak in the juices.
Strain the remaining broth to remove fat and solids, creating a clear au jus. Add more beef broth if needed to thin it.
Toast hoagie rolls with butter under the broiler for 1-2 minutes. Pile shredded beef onto each roll, top with provolone cheese, and broil for another 1-2 minutes until the cheese melts.