In a small bowl, combine the butter, garlic, herbs and spices until fully incorporated. Then, spread the butter mixture evenly over all sides of the meat.
Pour the beef stock at the bottom of a 6-quart or larger Instant Pot, and then place the trivet into the pot and place your roast on top. Lock on the lid, making sure the valve is set to seal. Cook on high pressure for 15 minutes, and after time is up, keep on warm for 30 minutes. If you're looking for medium-rare meat that is mostly pink with a red center, aim for a temperature of around 135 degrees F.
Once the roast is at your desired temperature, carefully open the Instant Pot and transfer the roast to a small baking sheet, allow to rest for 20 minutes before carving.
While the roast rests, remove the trivet from the Instant Pot and press the sauté button. In a small bowl, whisk together the cornstarch with a tablespoon of water. Bring the sauce to a simmer and stir in cornstarch mixture. Cook until the sauce has thickened. Give it a taste and adjust seasoning accordingly, adding more salt or pepper as needed.
Serve the roast sliced with the sauce spooned over.
Note: If you want to develop a golden brown crust on the roast, you can place it under the broiler, turning it on all its sides until fully browned all over.