Sear the roast: Turn the instant pot onto Sauté mode and add 1 tablespoon of oil. Once hot and shimmering (a drop of water should sizzle if added to the pot), add half of the roast in a single layer. Sear the roast on all sides (about 2 minutes for each batch) until nicely browned. Remove them to a plate. (Move them around when sautéing to avoid sticking)
Add more oil and sauté the rest of the roast. Remove the second batch of roast to the plate.
Deglaze: Add beef broth or water to deglaze the pot and scrape up every brown bit. This will avoid your pot from the “burning” warnings.
Add other ingredients: Add the au jus mix, ranch mix, and pepperoncini peppers. Add back the seared roast and butter.
Pressure cook the roast: Cover with the lid and close the steam valve. Turn off Sauté mode and set to “Manual” mode and “High Pressure” for 65 minutes.
Release the pressure: After the cooking cycle finishes, allow for a natural pressure release (about 15 minutes). After that, use the quick pressure lever to manually release any remaining pressure and turn off the pot.
Carefully remove the lid and transfer the roast to a plate.
Make the gravy: In a bowl, whisk together the cornstarch and water to create a slurry.
Add to the Instant Pot and set it to Sauté. Stir for a few minutes until the sauce thickens.
Drizzle the gravy over the roast to serve.