Set your Instant Pot to “Sauté” mode. Add oil and brown the beef chunks in batches. Remove and set aside.
Add diced onion and garlic to the pot. Sauté for 2–3 minutes.
Stir in tomato paste, thyme, rosemary, and Worcestershire (if using). Deglaze the pot with a splash of broth, scraping up any browned bits.
Return beef to the pot. Add carrots, potatoes, celery, and bay leaf. Pour in the rest of the beef broth.
Lock the lid. Set to “Pressure Cook” or “Manual” on HIGH for 35 minutes.
Allow natural pressure release for 15 minutes, then quick-release the remaining pressure.
(Optional) Mix arrowroot or cornstarch with 2 tbsp cold water and stir into the stew. Use “Sauté” to simmer for 5 minutes to thicken.
Taste and adjust salt/pepper. Remove bay leaf before serving.