Brown roast on all sides, by cooking on each side for about 5 to 6 minutes or until the roast browns.
Mix stew seasoning with water. Pour seasoning blend over the roast.
Place lid on Instant pot with the steam valve closed.
Select Instant Pot "manual" setting and set for 60-80 minutes on "high" pressure, 60 minutes for a 3 to 4-pound roast. 80 minutes for greater than 5 pounds.
Do a natural release for at least 10 minutes, then quick release, and remove the roast.
Peel and chop about 1 1/2 pounds of potatoes, and place into the Instant Pot. Steamer baskets are very handy for this!
Place lid on Instant pot with the steam valve closed.
Select Instant Pot "manual" setting and set for 6 minutes on "high" pressure.
When the potatoes have finished cooking perform a quick release. Remove potatoes from the Instant Pot.
If you want gravy, combine cornstarch and water together. Turn the Instant Pot to saute, and stir until the gravy thickens.
Standard Pressure Cooker Directions
Heat oil in pressure cooker bottom over medium-high heat. Brown chuck roast on both sides. Mix beef stew seasoning in water and add to meat. Add beef broth. Secure lid and reduce heat when the pressure regulator starts to rock.
Cook for 1 1/2 hours. While you can't do potatoes or vegetables with this method, I reduce some of the liquid after cooking, thicken for gravy and serve with mashed potatoes.