Place the oil in the bottom of the Instant Pot, and turn it on Saute HIGH.
Season the piece of beef well with the salt, pepper, onion powder, garlic salt, and seasoned salt.
Place the roast into the pre-heated Instant Pot, and let cook for 5-6 minutes, or until the bottom is well-browned.
Carefully flip the roast over onto the other side and brown that side well for another 5-6 minutes.
Place the sliced onion, carrots, onion soup mix, and beef broth into the pot. Stir to combine the soup mix with the broth. Close the lid, and turn the pot to high pressure and set the timer for 65 minutes.
When the timer goes off, allow the cooker to naturally release the pressure (NPR) for 15-20 minutes before venting.
Remove the lid after venting, and remove the roast from the pot. Scoop out the onions and carrots, and set aside on a platter with the roast. Cover with foil to retain heat.
Mix together the cornstartch and cold water. Turn the Instant Pot to HIGH saute again, and let the mixture in the pot bubble.
Whisk in slowly the cornstarch slurry. Start with half, stir constantly and let it thicken, and slowly add the rest if you'd like it thicker. The amount of liquid remaining in the pot will vary based on several different factor, so you might need more or less slurry to get to the thickness you prefer.
Serve with your favorite roast or mashed potatoes, crusty bread, and corn.
Notes
If you get a particularly tough roast, and it isn't fall-apart tender when you open the lid, don't be afraid to shut it again and do another pressure cycle. I recommend no more than 10 additional minutes at a time though. It can go from MEH to PERFECT very quickly in the IP!