Prepare the Roast: Liberally season the beef roast with salt and pepper. Set aside.

Sear the Meat: Heat olive oil in a cast iron skillet, Dutch oven, or Instant Pot (on sauté mode). Sear the roast on all sides until browned, about 3-4 minutes per side. Transfer to the slow cooker or set aside if using the Instant Pot.

Cook the Onions and Garlic: In the same pot, reduce heat to medium and add the sliced onions. Cook for about 5 minutes until softened. Stir in minced garlic and cook for another minute. Add a few tablespoons of the beef broth mixture and scrape up any browned bits with a wooden spoon.

Combine in the Slow Cooker: Place the seared roast and onion mixture into the slow cooker. Pour in the remaining beef broth mixture and add the bay leaf. Cover and cook on low for 5-6 hours or high for 3-4 hours, until the beef is tender.

Shred the Beef: Remove the cooked beef from the slow cooker and place on a cutting board. Shred with two forks or slice thinly against the grain. Return the meat to the slow cooker to soak in the juices.

Strain the Au Jus: Strain the cooking liquid through a fine mesh sieve into a bowl. Discard the bay leaf and reserve the au jus for dipping.

Assemble the Sandwiches: Toast the rolls in a 375°F oven until lightly crispy. Fill each roll with shredded beef and onions, then top with cheese slices. Return to the oven or broiler for 2-3 minutes to melt the cheese.

Serve: Serve the sandwiches with a small bowl of au jus on the side for dipping. Enjoy immediately.