Set your Instant Pot to sauté mode. Once hot, add olive oil and sear the chuck roast on all sides until browned. Remove and set aside.
Add sliced onions and cook for about 8 minutes until softened and slightly golden. Stir often to keep them from sticking.
Stir in garlic, tomato paste, Worcestershire sauce, thyme, salt, and pepper. Cook for 2 minutes.
Pour in beef broth, scraping the bottom of the pot with a wooden spoon to deglaze.
Return the roast to the pot. Lock the lid, set to sealing, and pressure cook on high for 60 minutes.
Let the pressure release naturally for 15 minutes, then quick release any remaining pressure.
Remove the roast and rest it for 10 minutes before slicing.
Optional: Set Instant Pot to sauté, stir in a cornstarch slurry (cornstarch + water) to thicken the sauce. Simmer until desired consistency.