Turn on your instant pot and set it to "saute". In a small bowl stir together salt, pepper, garlic powder, onion powder, and smoked paprika. Rub mixture all over the roast to coat all sides.
Drizzle oil in instant pot, wait about 30 seconds, then use tongs to place roast in the pot. Do not move it for 3-4 minutes until well-seared and browned. Use tongs to turn the roast onto another side for 3-4 minutes, repeating until all sides are browned.
Switch instant pot to "pressure cook" on high and set to 60-80 minutes (60 for a 3 pound roast, 80 for a 5 pound roast. see notes if using baby carrots). Add potatoes, onions, and carrots to pot (just arrange them around the roast) and pour beef broth and worcestershire sauce over everything. Place lid on the pot and turn to locked position. Make sure the vent is set to the sealed position.
When the cooking time is up, do a natural release for 10 minutes (don't touch anything on the pot, just let it de-pressurize on it's own for 10 minutes). After 10 minutes, turn vent to the venting release position and allow all of the steam to vent and the float valve to drop down before removing the lid.
Transfer the roast, potatoes, onions, and carrots to a platter and shred the roast with 2 forks into chunks. Use a handheld strainer to scoop out bits from the broth in the pot. Set instant pot to "soup" setting. Whisk together the water and corn starch. Once broth is boiling, stir in corn starch mixture until the gravy thickens. Add salt, pepper, and garlic powder to taste.
Serve gravy poured over roast and veggies and garnish with fresh thyme or parsley if desired.
If you'd like to use baby carrots, keep in mind that they will cook much faster than large chunks of whole carrots. To make sure they don't turn to mush, set your pressure cooking time 10 minutes shorter than the recipe states and leave the carrots out of the pot. Once the pressure cooking time is finished, add baby carrots to the pot and set the pot to pressure cook for 10 more minutes.
The recipe is written for a thawed roast. If using a frozen roast, you will need to add about 20-30 minutes to your pressure cooking time. You can also skip the searing step and simply rub the spices on the roast and then place it in the pot and then move ahead to the pressure cooking step.