Preheat the oven to 275 degrees
Season the roast on all side with kosher salt and black pepper. Dust with flour.
Make the ranch dressing by whisking the mayo, brine, dill, and paprika together in a small bowl. Whisk in the buttermilk and let chill for a few minutes to allow the flavors to incorporate.
Heat the oil in a Dutch oven set over medium-high heat. When the oil is just smoking, add the roast to the Dutch oven and brown well, about 5 minutes per side.
Pour the ranch dressing over the roast. Cut the butter into eight slices and place the slices on and around the roast. Add the pepperoncini to the Dutch oven and cover.
Transfer the Dutch oven to the preheated oven and cook for 5 to 6 hours. Turn the roast every hour or so, and if necessary, add a little bit of beef broth if it appears the roast is drying out.
After six hours, test the roast for doneness. It should shred easily. Use two forks to pull the roast apart and incorporate the meat with the gravy in the bottom of the Dutch oven. Garnish with fresh pepperoncini and serve.