Season the beef. Place the chuck roast into the slow cooker. Sprinkle evenly with Italian seasoning, garlic powder, onion powder, salt, and pepper.
Add the liquids and peppers. Pour the beef broth into the slow cooker. Drain the pepperoncini, reserving ½ cup of the juice, and add it in with the broth. Add half of the peppers to the slow cooker and store the remaining peppers in the refrigerator to use later.
Cook low and slow. Cover and cook on low for 8–10 hours or high for 5–6 hours. The beef is ready when it easily shreds with a fork. If you have the time, cooking on low will give you the best results and help keep the beef tender and juicy.
Shred the beef. Remove the beef from the slow cooker and place it into a large bowl. Use two forks to shred the meat.
Add flavor back in. Stir in the remaining reserved pepperoncini and spoon some of the cooking juices over the shredded beef. Return to the slow cooker if desired to keep warm. Taste and adjust seasoning as needed.