Turn the sauté feature on your instant pot or slow cooker and add in 1 tablespoon of oil.
In a small bowl, combine the flour, salt, and pepper.
Lightly coat each piece of beef with the flour mixture, making sure to remove any excess, and place in the heated instant pot. Arrange the pieces an inch or so apart. You may have to work in batches. Sear on 2 sides for 3-5 minutes, or until browned. Remove and set aside. Repeat with another tablespoon of oil each time until all of the meat is browned. Reserve any leftover flour mixture.
Add in 1 tablespoon of oil, followed by the diced onion, carrots, celery, and garlic. Cook for 3-5 minutes, or until the onion is tender and translucent, Scraping the bits at the bottom of the pot as well.
Add in the leftover flour mixture (about 1 tablespoon worth) and the tomato paste. Cook for 1 minute.
Stir in the worcestershire and red wine.
Then stir in the stock.
Add in the potatoes, browned meat, and mushrooms.
Set your slow cooker on high for 4 hours or low for 6-8 hours.
Season with salt and pepper if needed. Serve.