Pat the chuck roast completely dry with paper towels and season with black pepper.
Sear the roast in a skillet with hot oil for 3-4 minutes on each side until browned.
Place the seared roast in a slow cooker and sprinkle ranch seasoning and au jus mix on top without mixing.
Nestle whole pepperoncini peppers around the roast and place the stick of butter on top.
Cover and cook on low for 8 hours without lifting the lid.
After cooking, shred the roast using forks and mix with au jus; skim excess fat before serving.