1. Turn on the Instant Pot and select the 'Sauté' function.
2. Add a bit of oil and sauté the onions, carrots, and celery for about 5 minutes.
3. Add the garlic and sauté for another minute.
4. Add the chicken breast, chicken broth, salt, pepper, and thyme.
5. Close the lid and set the Instant Pot to 'Manual' for 10 minutes.
6. Once the cooking time is up, let the pressure release naturally for 10 minutes, then quick release any remaining pressure.
7. Remove the chicken breast, shred it, and return it to the pot.
8. Stir well and serve hot.