Gather all ingredients.

Heat 2 tablespoons oil in a multi-functional pressure cooker (such as Instant Pot) set to the Sauté function. Add roast to hot oil and cook until browned all over, 4 to 5 minutes per side. Pour in broth.

Combine potatoes, carrots, onion, soup mix, and remaining 2 tablespoons oil in a resealable plastic bag. Seal the bag and shake until vegetables are evenly coated.

Pour mixture into the pressure cooker and spread out evenly.

Close and lock the lid. Select high pressure according to the manufacturer's instructions; set the timer for 60 minutes. Allow 10 to 15 minutes for the pressure to build. Release the pressure carefully using the quick-release method according to the manufacturer's instructions, about 5 minutes. Unlock and remove the lid.

Transfer roast and vegetables to a serving platter, leaving drippings in the pot.

Select the Sauté function and bring drippings to a boil. Combine water and cornstarch in a bowl; pour into the drippings. Cook, stirring frequently, until gravy is slightly thickened, 2 to 3 minutes. Season with garlic salt and pepper. Slice roast and serve with vegetables and gravy.