Season the chuck roast with salt and black pepper on all sides.
In a large skillet, heat a tablespoon of oil over medium-high heat. Sear the beef on all sides until browned (about 4-5 minutes per side), then transfer to the crockpot. Searing adds extra flavor but can be skipped if short on time.
In the crockpot, layer the sliced onions and minced garlic on top of the beef.
In a bowl, combine beef broth, Worcestershire sauce, thyme, and additional salt and pepper. Pour this mixture over the roast and onions in the crockpot.
Cover the crockpot and set it to low heat. Cook for 8-10 hours, or until the beef is tender and easily pulls apart with a fork.
Once cooked, remove the roast from the crockpot and shred it using two forks. Return the shredded beef to the crockpot, mixing it with the broth and onions.
While the beef is in the crockpot, you can heat the hoagie rolls if desired. Optionally, place slices of provolone cheese on the rolls and broil them in the oven until bubbling and golden.
Using tongs, load the shredded beef onto the hoagie rolls, spooning some of the broth and onions onto each sandwich.
Ladle some of the broth into small bowls as a dipping sauce for the sandwiches. Garnish with fresh parsley if desired.
Notes
Searing the beef is optional but adds extra flavor.