Place the beef roast into the base of the slow cooker and pour the beef stock around it.
Sprinkle the ranch dressing mix directly onto the beef roast, coating it well. Add the butter, cut into 4 "pads" directly onto the ranch-coated beef roast.
Place the pepperoncini peppers on top of the beef roast. If you are adding potatoes and/or carrots, place them around and on top of the beef roast as well.
Set on low and cook for 8 hours.
Remove the roast from the slow cooker and slice or shred the meat. If desired, strain 1 cup of the liquid and skim off the fat. Place in small saucepan and thicken with 1 to 2 Tbsp cornstarch to make gravy.
Serve Mississippi Beef Roast with potatoes, carrots, salad or other favorite side dish.