Add the olive oil to the Instant Pot inner cooking pot and select the "Sauté" function. Adjust the power to high (by pressing "More").
When the oil is hot add the beef roast and sprinkle the salt and pepper over it to season. Sear the roast on all sides, approximately 3-4 minutes per side. Remove roast from Instant Pot and transfer to a plate. Set aside.
Add the beef broth, then deglaze the inner pot by gently scraping the bottom with a rubber spatula to release any brown bits. Add the tomato paste, herbs, and garlic powder, and stir to combine. Press the Cancel button to end the Sauté program.
Place the beef roast in the Instant Pot. Add the lid and lock it into place with the vent set to "Sealing". Select the "Pressure Cook" or "Manual" function and adjust to "High". Set the cooking time to 60 minutes.
While the beef is cooking prepare the vegetables.
When cook time has finished, allow the pressure to release naturally for 10 minutes before doing a quick release on any remaining pressure. Add onion, carrots, potatoes, and green beans on top of the roast.
Put the lid back on and lock into place with the vent set to "Sealing". Press the "Pressure cook"/ "Manual" button (check it is still set to "High"), and set to pressure cook for 3 minutes.
When cooking time is has finished, allow the pressure to release naturally for 5 minutes before doing a quick release on any remaining pressure.
Carefully remove the lid and transfer roast and vegetables to a serving plate and cover with foil while you make the gravy
Make a slurry with the cornstarch mixed with a little cold water. Switch the Instant Pot to "Saute", and slowly add the cornstarch slurry to the liquid in the Instant Pot. Allow it to simmer, stirring frequently for around 5 minutes until the gravy has thickened to your liking.
Serve chuck roast and vegetables smothered in the gravy. Enjoy!
Notes
Chuck roast is best for this recipe, but you can use brisket or blade roast.
Prep the vegetables after the roast starts cooking.
Cornstarch is also known as cornflour in the UK, Australia and NZ. Note: this is not the same as corn flour in the US.