In a small bowl, mix together garlic powder, onion powder, dried Italian seasoning, crushed red pepper flakes, black pepper, salt, and smoked paprika.
Rub the spice mixture evenly all over the beef chuck roast.
Heat olive oil in a large skillet over medium-high heat. Sear the beef roast on all sides until browned, about 3-4 minutes per side.
Transfer the seared beef roast to the slow cooker.
Add beef broth, water, Worcestershire sauce, minced garlic, sliced pepperoncini peppers with juice, sliced green bell pepper, and sliced onion to the slow cooker.
Cover and cook on low for 8 hours, or until the beef is very tender and shreds easily with a fork.
Remove the beef from the slow cooker and shred it using two forks.
Return the shredded beef to the slow cooker and stir to combine with the juices and vegetables.
Cook uncovered on low for an additional 15-20 minutes to allow the flavors to meld and the sauce to thicken slightly.
Serve the Italian beef hot on sandwich rolls or over your favorite side dish.