Season and Prepare the Meat
Place the roast on a clean cutting board. Generously season all sides with kosher salt and freshly ground black pepper. Sprinkle the surface with all-purpose flour, ensuring an even coating, and gently massage it into the meat.
Sear the Roast
Heat neutral oil in a large sauté pan over high heat until shimmering. Place the seasoned roast in the pan and brown each side for 4 to 5 minutes, creating a golden crust. Remove the roast from the pan and transfer it to the bowl of a slow cooker. Add unsalted butter and pepperoncini peppers atop the meat. Secure the lid and set the slow cooker to the low setting.
Prepare and Add the Ranch Dressing
While the roast begins cooking, combine mayonnaise, apple cider vinegar, dried dill, and sweet paprika in a small mixing bowl. Whisk the ingredients until smooth, incorporating buttermilk if desired for added creaminess. Remove the slow cooker's lid and pour the dressing over the roast. Replace the lid and continue cooking undisturbed for 6 to 8 hours, or until the meat becomes tender enough to shred effortlessly with two forks.
Finish and Serve
Gently shred the cooked roast, mixing it thoroughly with the surrounding gravy. Garnish with freshly chopped parsley. Serve alongside mashed or roasted potatoes, over egg noodles, or on soft sandwich rolls, as preferred.