Set a 6-qt Instant Pot® to the high saute setting. Heat oil; add beef and cook until evenly browned, about 2-3 minutes per side; set aside.
Stir in beef stock, scraping any browned bits from the bottom of the pot.
Stir in pepperoncini salad peppers and liquid, dry onion soup mix, parsley flakes, chives, dill, onion powder, garlic powder and pepper. Return beef to the pot.
Select manual setting; adjust pressure to high, and set time for 45 minutes. When finished cooking, naturally release pressure according to manufacturer’s directions, about 20-30 minutes.
Remove beef from the Instant Pot®; shred, using two forks.
In a small bowl, whisk together cornstarch and 3 tablespoons cold water; set aside.
Select high sauté setting. Bring to a boil; stir in cornstarch mixture and cook, stirring frequently, until slightly thickened, about 3-5 minutes. If the mixture is too thick, add more beef stock as needed until desired consistency is reached.
Serve beef with juices immediately.
Notes
Avoid lean cuts. Choose heavily-marbled chuck roast so the fat can melt into juicy, tender, shreddable meat.
Sear the meat. Browning the beef first is key here. That dark crust on the chuck roast will create such richer, deeper flavors (plus, the browned bits stuck to the bottom of the Instant Pot add so much flavor).
Deglaze the pot. Add the beef stock and scrape up all the browned bits stuck to the bottom to build deep flavors and to prevent the dreaded burn notice.
Naturally release pressure. Once the pot roast is finished cooking, let the Instant Pot release pressure naturally, about 20-30 minutes. This will let the meat rest while keeping it moist and tender.
Serve with crusty bread. Serve with all the homemade crusty bread for dipping, sopping and dunking!
Freeze as needed. Let cool completely and portion into plastic freezer bags in individual servings with the cooking juices. Reheat in the oven at 350°F, covered in aluminum foil (to retain moisture) until warmed through, adding a splash of beef broth to prevent dryness.