Cut the roast into 4 quarters and season with salt and pepper.
Heat the Instant Pot using the "sauté" function on the highest setting. When the screen reads "hot" add the avocado oil.
Add the roast to the pot, 2 pieces at a time, and sear until a brown crust forms. Remove from the pot and set aside. Press the "cancel" button.
Add the beef broth to the pot and scrape any browned bits from the bottom. Add all of the roast back to the pot, place the lid, and set the valve to "sealing." Press the "meat" function and adjust the time to 45 minutes.
When the cooking time is finished, let the pot naturally release the pressure for 10 minutes, then release the rest of the pressure using a quick release.
Remove the lid and check the roast. If it shreds easily, it is finished. If it is still tough, place the lid back on and set the timer for 15 additional minutes, followed again by a 10 minute natural release. Cooking time will depend on the size of the roast. If you are having trouble getting the lid back on, run the underside under cold water for a few seconds to cool it down.
After the roast is finished, remove it to a plate and set aside (leave the juices in the pot for the gravy).
For the gravy, set the Instant pot back on sauté and add the butter and flour or xanthan gum. Whisk thoroughly so there are no lumps and bring to a boil. If the gravy seems too thick, add beef broth a little at a time until it is your preferred thickness. Taste for seasoning and add salt an pepper if necessary.