Preheat your oven to 350°F.
Heat a large, oven-safe Dutch oven or heavy-bottomed pot over medium-high heat. Add the vegetable oil and allow it to heat up.
Season the chuck roast with flake salt on all sides. Sear the roast in the hot oil until it's well-browned on all sides. This should take about 3-4 minutes per side.
Add all of the pepperoncini peppers with the brine to the pot . (You can use as many or as few peppers as you prefer for your desired level of spiciness. If you like it milder, use fewer peppers; for more heat, use more.)
In the same pot, add the Ranch Seasoning, Italian Herbs, and the beef stock. The liquid should come about halfway up the sides of the roast. If needed, add more beef stock or water.
Cover the pot with a lid and place it in the preheated oven. Allow the roast to braise for 2-2.5 hours, or until the meat is tender and easily shreds with a fork.
Remove the Mississippi Pot Roast from the oven and use two forks to shred the meat right in the pot. The peppers and juices will add flavor and make the shredded meat juicy.
Serve the shredded Mississippi roast with the flavorful juices and peppers over mashed potatoes, or as a filling for sandwiches in hoagie rolls.