Pat chicken breasts dry and season evenly with 1/2 tsp salt and 1/4 tsp black pepper. Heat 1 tbsp olive oil in a large Dutch oven or pot over medium-high heat. Add chicken breasts and sear for 4-5 minutes per side, until golden brown and cooked through. Remove chicken from the pot and set aside to cool slightly. Once cool enough to handle, shred the chicken using two forks or your hands.

Reduce heat to medium. Add another 1 tbsp olive oil to the same pot. Add diced onion, carrots, and celery. Sauté for 5-7 minutes, stirring occasionally, until vegetables start to soften. Add minced garlic and cook for another 1 minute until fragrant.

Pour in the chicken broth. Add the rinsed long-grain white rice, bay leaf, dried thyme, and dried oregano. Bring the soup to a boil, then reduce heat to low, cover, and simmer for 15-20 minutes, or until the rice is tender. Stir occasionally to prevent rice from sticking to the bottom.

Remove the bay leaf. Stir in the shredded chicken and fresh lemon juice. Heat through for 2-3 minutes. Taste the soup and adjust seasoning with additional salt and black pepper as needed.

Ladle the hot soup into bowls and garnish generously with fresh chopped parsley before serving.