Dredge the beef in flour on all sides. Add 1 tbsp of the oil to your Instant Pot. Press the "sauté" button and once the oil is hot, add the beef. Brown the beef on all sides (I find this easiest to do with tongs). I like to do 2 batches so the meat isn't crowded and browns nicely.
Once the beef is nicely seared, take it out of the Instant Pot and set aside. I add the second tablespoon of oil before browning the second batch.
While the beef is browning, I like to do the onions/celery/carrots/potato chopping, but if you prefer to prep everything beforehand, that is fine too.
When the second batch of beef is browned, take it out of the Instant Pot. Add the onion and sauté for 3-4 minutes.
Add the beef broth, tomato paste, Dijon mustard, Worcestershire sauce, and garlic to the Instant Pot. Be sure to scrape up the brown bits from the bottom (I use a wooden spoon). Give it a good stir.
Add the remaining ingredients. The Instant Pot will be quite full, but it should not go over the maximum capacity line.
Close the lid and set the valve on "sealing", and cook on high pressure for 35 minutes. It will take 10-15 minutes for the Instant Pot to get up to pressure.
Once the countdown is done, I usually do a quick release if I'm in a rush. A natural pressure release (even partial) definitely won't hurt since the potatoes and carrots are already pretty soft in this dish, and it will leave everything even more tender. Season with salt & pepper as needed, and enjoy! Recipe freezes well.