Place the chuck roast into the bottom of a 5- or 6-quart slow cooker. Do not add any water or broth.
Sprinkle the ranch seasoning packet evenly over the top of the roast, then sprinkle the au jus packet on top.
Lay the butter pats over the seasoning. Add the whole pepperoncini peppers around and on top of the roast. Pour the 2 tablespoons of pepperoncini brine over everything.
Cover and cook on LOW for 8–10 hours or HIGH for 5–6 hours. Do not open the lid during cooking.
When the beef is completely fall-apart tender, shred it right in the slow cooker using two forks. Toss the shredded meat with the cooking juices.
Taste the gravy before serving. Adjust salt only if needed.
Serve over mashed potatoes, egg noodles, rice, or on crusty rolls with a spoonful of the cooking juices.