Season the roast generously with salt and pepper.
In a large measuring cup, mix the beef broth and Worcestershire sauce. Set aside.
Heat the olive oil in a large skillet or Dutch oven (or an Instant Pot on sauté) over medium-high heat. Sear the roast on all sides until well browned, then move it to the slow cooker (or leave it in the Instant Pot).
Turn the heat to medium and add the onions to the same pot. Cook for 5 minutes, adding a little more oil if needed. Add the garlic and cook for 1 to 2 minutes more. Pour in a couple of tablespoons of the broth mixture and scrape up the browned bits from the bottom.
Slow cooker: add the onion mixture and juices to the slow cooker with the rest of the broth and the bay leaf. Cover and cook on HIGH for 3 to 4 hours or LOW for 5 to 6 hours, until the meat is tender. Instant Pot: add the rest of the broth and the bay leaf, seal and cook on high pressure for 60 minutes, then let the pressure release naturally for 20 minutes.
Lift out the roast and slice it thinly against the grain, or shred it.
Strain the cooking liquid through a fine mesh strainer into a bowl. This is your au jus. Discard the bay leaf and set the onions aside.
Return the meat and onions to the pot and moisten with a little au jus. Season with salt and pepper. Keep the rest of the au jus for dipping, stretching it with a little extra beef broth if you want more.
Toast the rolls and fill them with the meat and onions. Top with cheese and melt it in a 375°F oven or under the broiler for a few minutes.
Serve with the au jus on the side for dipping.