Step 1Add the chuck roast to a slow cooker. Place a 3- to 4-pound boneless beef chuck roast in a 6-quart or larger slow cooker.Step 2Add the seasoning packets. Sprinkle the chuck roast with 1 packet ranch salad dressing and seasoning mix and 1 (1-ounce) packet au jus gravy mix.Step 3Add the butter, pepperoncini, and brine. Cut 1 stick butter into cubes and place on top of the roast. Pour 1/2 cup brine from a jar of pepperoncini peppers and pour this over the roast. Add 10 to 12 pepperoncini peppers.Step 4Cover and cook on LOW for 8 hours. Cover and cook until the beef is very tender, about 8 hours on the LOW setting, or 5 to 6 hours on the HIGH setting.Step 5Use tongs to shred the roast and serve. Shred the roast into bite-sized pieces with tongs. Serve the pot roast over mashed potatoes or pile onto rolls and top with provolone cheese.