Pat the chuck roast dry with paper towels. Mix salt, pepper, oregano, basil, and garlic powder in a small bowl, then rub all over the roast. Let sit at room temperature while you prep the slow cooker, about 15 minutes.

Whisk beef broth, Italian dressing mix, and pepperoncini juice in the slow cooker insert until dissolved. Add the pepperoncini peppers. Nestle the seasoned roast into the liquid, turning once to coat.

Cover and cook on LOW for 8 to 10 hours, or until the beef shreds easily with a fork. The meat should feel completely tender and offer no resistance when prodded. If time is short, cook on HIGH for 5 to 6 hours, though low yields more tender results.

Transfer the roast to a large bowl, leaving the cooking liquid in the slow cooker. Shred with two forks, discarding any large pieces of fat or connective tissue. Return the shredded beef to the slow cooker and stir to combine with the juices. Let rest on WARM for 15 minutes so the meat soaks up the broth.

Pile beef high on split rolls. Top with giardiniera and provolone if using. For extra authenticity, ladle a spoonful of the hot cooking liquid (au jus) into a small bowl for dipping, or spoon directly over the meat if you prefer it wet.