Take a paper towel and make sure you dry both sides of the roast.Heat the oil in a large skillet set over high heat. You want it really hot here to brown the beef quickly.Place the roast in the pan and brown on all sides, 4 to 5 minutes a side, to create a crust. Remove roast from pan and place it in the bowl of a slow cooker.Pour pepperoncini juice over the roast. Next, sprinkle packets of dry ranch dressing and au jus mix. Cut up butter and place on top. Top with pepperoncini.Cook for 8-10 hours on low. Once tender, remove the roast and shred using two forks. Return to the slow-cooker and stir well. Serve on a bun or on top of mashed potatoes.