Bring chuck roast to room temperature, then season well with salt and pepper.
Heat the Instant Pot using the sauté setting. Once hot, add oil, then sear roast on both sides. Set aside.
Add 1 onion and celery to pot and cook for 2 minutes, until soft and translucent. Then add garlic, thyme, rosemary, and bay leaf - continue cooking for 1 minute.
Add red wine to deglaze the pot, making sure to scrape up all bits. Let wine simmer for at least 2 minutes.
Add roast, then add enough broth so that the roast is just barely covered.
Lock lid and cook for 75 minutes at high pressure. Once time is complete, let pressure naturally release (about 30 minutes).
Carefully remove roast and set aside to rest.
Using a fine mesh strainer, pour liquid into separate container, then return to pot. Discard aromatics.
Add sliced onion, carrots, and potatoes to pot and close lid.
Lock lid and cook for 4 minutes at high pressure, then quick-release pressure.
Meanwhile - In a small dish, combine cornstarch and water. Once cook time is complete, open lid, switch to sauté setting, and add cornstarch slurry to pot. Cook until desired consistency is achieved (2-3 minutes).
Return roast to pot and pull apart meat as much as you like.
Serve together and enjoy!