Heat olive oil in a large stockpot over medium heat.
Add diced onion, carrots, and celery, sautéing for 5 to 7 minutes until vegetables are softened.
Add minced garlic and cook for 1 minute until fragrant.
Pour in chicken stock, dried thyme, and the bay leaf, then bring the mixture to a boil.
Place whole chicken breasts into the boiling broth, reduce heat to low, cover, and simmer for 20 minutes.
Remove the chicken breasts from the pot, shred using two forks, and set aside.
Add the uncooked rice to the pot, cover, and continue to simmer for 15 to 20 minutes until the rice is tender.
Return the shredded chicken to the pot and stir in the fresh parsley and lemon juice.
Remove the bay leaf and season with salt and black pepper to taste before serving.