Pat the roast dry and cut 6 1-inch deep slits in the top. Peel the garlic cloves and cut them in half. Stuff each slit with a half clove of garlic and a piece of cut rosemary spring. Season all over with the salt and black pepper. In the bottom of an Instant Pot or similar electric pressure cooker or multi-cooker, pour in the water, then add the beef, nestling the pieces in snuggly. Arrange the potatoes on top of the beef. Mince the remaining garlic and scatter on top of the potatoes. Sprinkle the chopped rosemary all over the potatoes and beef. Then, sprinkle a pinch of salt on top of the potatoes. Pour the tomato sauce and Worcestershire over the beef. Cover and seal the Instant Pot. Cook on Manual/High Pressure for 60 minutes. It will take 10 to 15 minutes for the Instant Pot to come to pressure, then the countdown will begin. When the cook time has elapsed, allow the pressure to release naturally for 10 minutes, then quick release any remaining pressure. Carefully open the lid and add the baby carrots on top. Reseal the lid and cook on Manual/High Pressure for 5 minutes more. Let the pressure release naturally for 10 minutes (this natural release is KEY for a tender roast). Quick release any remaining pressure. With a slotted spoon, remove the meat and vegetables to a large platter or bowl, discarding any large pieces of fat. Make sure the Instant Pot is off. In a small bowl, briskly whisk together the slurry of 2 tablespoons cornstarch and 2 tablespoons water until smoothly combined. While whisking the cooking juices in the Instant Pot, slowly pour in the slurry. Turn the pot to SAUTE, then cook, stirring frequently, until the juices have thickened into a thin gravy, about 3 to 5 minutes. Turn off the Instant Pot. Add the beef and vegetables back to the pot and stir to warm through (the potatoes, veggies, and meat will all break down a little and be tender and delicious). Serve hot, ensuring each serving gets a little bit of everything.
