Season meat with salt and pepper.
Select sauté function of Instant Pot, add 1 tablespoon of oil and wait until it says hot.
Then sear the meat for 5 minutes on each side, until browned.
Remove meat from the pot and set aside.
Add remaining oil, scraping the bottom of the Instant Pot to remove any bits of meat stuck on.
Then sauté the onions for 5 minutes before stirring in the garlic for 30 seconds.
Cancel the sauté function and deglaze the insert with 2 tablespoons of stock.
Add in the meat, mushrooms, carrots, beef stock, balsamic vinegar, anchovies, mixed herbs and thyme sprigs. Season with any salt and pepper if needed.
Cover the Instant Pot, select manual pressue / high pressure and set the timer for 50 minutes. When done allow for a complete natural pressure release (if not cooked through, cook for another 5-10 minutes).
Remove the pot roast from Instant Pot, slice or shred, and serve with the vegetables and sauce poured over top.
(Optional step) Make gravy using the cooking liquid. To thicken, create a corn flour paste with 1 tablespoon corn flour and 2 tablespoons water. After the roast is cooked, remove meat, add the paste to the insert and sauté until it reaches the desired thickness.