Take the beef out of the refrigerator and season it generously with salt, pepper, and garlic powder. Let it come to room temperature if possible.
Set your Instant Pot to sauté mode. Heat one tablespoon of olive oil and add half of the seasoned stew meat. Sear each side for about three minutes until nicely browned. Remove and repeat with remaining meat.
Pour in half a cup of broth and scrape up any browned bits from the bottom of the pot.
Add back all seared meat along with potatoes, carrots, onion, celery, minced garlic, Italian seasoning, Worcestershire sauce, three cups of broth, and apple vinegar. Stir until well mixed.
Lock on the lid and set the valve to seal. Cook on high pressure for 30 minutes.
Allow the Instant Pot to naturally release pressure for about ten to fifteen minutes.
Whisk together four tablespoons of cornstarch with four tablespoons of broth in a small bowl until smooth.
Quickly release any remaining pressure and turn the pot back onto sauté mode. Pour in the prepared slurry while stirring until thickened, about two to three minutes.