Place the sliced onions in the bottom of the slow cooker and set the chuck roast on top.
Whisk together the garlic, beef consommé, beef broth, soy sauce, Worcestershire sauce, thyme, and pepper in a bowl, then pour over the meat.
Cook on Low for 8 hours until the meat is very tender and easily falls apart.
Remove the meat to a cutting board, shred it with two forks, and return it to the broth briefly to absorb flavor.
Ladle the broth into small cups for dipping, using a slotted spoon to keep the meat separate.
Assemble the sandwiches by placing the beef on split hoagie rolls, topping with provolone, and broiling for 1 to 2 minutes until the cheese is melted.
