Set your Instant Pot to sauté mode and allow it to preheat. While it heats, season the beef with salt and pepper. Add 1 Tablespoon of olive oil and place the meat in the pot. Cook for around 1 minute on all sides until the meat is well browned, then transfer it to a plate.
Add more oil if needed, then add the onions, carrots, and celery and cook for 3-4 minutes, stirring occasionally, until softened. Turn off the heat, then add the garlic and cook for another minute.
Add ½ cup of beef stock and scrape up any brown bits from the bottom of the pot with a wooden spoon.
Add the meat back to the pot along with any juices that have collected on the plate. Then add the remainng beef stock, potatoes, and herbs. Close the lid and set the Instant Pot to manual high pressure for 65 minutes.
After the cooking cycle has completed, allow the pressure to release naturally for 10 to 15 minutes, then vent the remaining pressure completely before removing the lid.
Remove the meat and vegetables and set them on a platter, then use a handheld mesh strainer to strain the cooking liquids. Alternatively, you can pour the liquids through a mesh strainer into a large bowl, then pour them back into the pot.
Set the Instant Pot to sauté mode. While it heats, mix the cornstarch and water in a cup or bowl to form a slurry then add it to the cooking liquid. Bring to a simmer and cook for 2-3 minutes, stirring frequently, until thickened, then turn off the pot.
Break the meat up into chunks then top with the gravy and serve.
Notes
Cooking TimeThe 65 minutes of pressure cooking time in this recipe is for a 3 pound roast. Add or subtract 10 minutes per pound if your roast is a different size.The pressure cooking time also does not account for the time it takes for the pot to reach full pressure. This can add another 10-15 minutes to the actual cooking time depending on your pressure cooker.This recipe is written for a thawed roast. For a frozen roast, skip the searing step and add an additional 30 minutes of cooking time.