Season and sear the roast: Pat the chuck roast dry and season it all over with the salt and pepper. Heat the oil in a large skillet over medium-high heat and sear the roast 4-5 minutes per side, until it's well browned and lifts off the pan on its own.

Load the slow cooker: Scatter the sliced onion across the bottom of a 6-quart slow cooker and set the seared roast on top of it. The onion keeps the meat off the hot floor of the crock.

Add the liquid and peppers: Sprinkle the Italian dressing mix and Italian seasoning over the roast. Pour in the beef broth, then add the drained pepperoncini and 1/2 cup of their brine.

Cook on low for 9 hours: Cover and cook on low for 9 hours. It's done when a fork twists in the meat with no resistance and a thermometer in the center reads 200-205°F. That's well past the USDA's 145°F minimum for whole cuts of beef, and it has to be, because chuck doesn't shred until the connective tissue melts up around 200°F.

Shred and soak: Lift the roast onto a cutting board, shred it with two forks, and discard any big pockets of fat. Return the beef to the crock, stir it into the juice, and let it sit on warm at least 20 minutes so it drinks the liquid back up.

Toast the rolls: Split the hoagie rolls, lay them cut side up on a sheet pan, and broil 1-2 minutes until lightly golden. Watch them closely, they go from toasted to burnt fast.

Build the sandwiches: Lay a slice of provolone in each roll, pile the beef in with a slotted spoon, and top with giardiniera. Spoon extra juice over the top, or pour it into small bowls for dipping.