Press the Saute button on the Instant Pot and allow it to get hot.
Add olive oil, then sear pot roast on all sides.
Remove roast from Instant Pot and use the beef broth to deglaze the pan by stirring with a wooden spoon.
Transfer beef roast to Instant Pot, add all other ingredients except for the Xanthan Gum, and bring to a boil.
Turn Instant Pot off, then secure the lid in place,
Press manual high pressure and use the up bottom to program 90 minutes.
It will take several minutes for the Instant Pot to come to pressure. When it does, it will begin to count down from 90 minutes.
Once the time is complete, let it naturally release for 15 minutes, then quick release.
Once the pin has dropped, remove the lid and use a fork to shred.
Turn Instant Pot to warm and sprinkle 1/2 teaspoon of Xanthan Gum to thicken the gravy. Allow the roast to sit for 10 minutes or until the sauce has thickened before serving.