Turn on the Instant Pot to SAUTÉ and add 1 tbsp of avocado oil.
Cut the chuck roast into 4 equal pieces and generously season with salt and pepper.
Once the Instant Pot indicates that it's "hot," add the meat pieces and sear for 2-3 minutes on each side until browned. Remove the meat and set aside on a plate.
Add the remaining 1 tbsp of avocado oil and add garlic, onion, rosemary, and thyme. Sauté for 5 minutes until fragrant and the onion is translucent.
Add bone broth, coconut aminos, and tomato paste, and scrap the bottom of the pot with a wooden spoon. Turn off the Instant Pot.
Add the meat pieces back in, then add radishes and carrots on top of the meat. It's okay if some vegetables fall into the broth.
Screw on the lid to the Instant Pot, make sure the pressure valve is set to SEALING, then cook on MANUAL for 40 minutes. Once it beeps to a finish, let the pressure release naturally for 10 minutes before opening the valve manually.
Open the lid, then use a slotted spoon to remove the veggies and the meat to a separate plate. Shred the meat into bite-sized pieces.
Turn the Instant Pot on to SAUTÉ with the broth in it, then whisk together xanthan gum (or arrowroot starch) and 2 tbsp of water in a separate bowl. Add this roux mixture into the broth.
Let the broth simmer for about 3 minutes until thickened to your liking and turns to gravy.
You can add the meat and veggies back into the gravy to heat up before serving, or plate the meat and veggies and serve with the gravy on the side to drizzle over the meat. Garnish with parsley flakes, if desired.