Chop carrots, celery, and onion into small, even pieces on your chopping board. Rinse the rice under cold water until the water runs clear and set aside.
Heat a large pot over medium heat and add a tablespoon of oil. Once shimmering, add the diced onion, carrots, and celery. Cook, stirring occasionally, until fragrant and slightly softened, about 5 minutes.
Push the vegetables to the side of the pot, then add the diced chicken to the cleared space. Brown the chicken until golden, about 7 minutes, stirring occasionally to prevent sticking.
Pour in the chicken broth and add the rinsed rice. Bring the mixture to a boil over high heat, then reduce the heat to low and cover the pot. Let it simmer gently for about 20 minutes, or until the rice is tender and the chicken is cooked through.
Uncover the pot and taste the broth, adding salt and pepper as needed. Stir in the freshly squeezed lemon juice to brighten the flavors.
Chop the fresh parsley or dill and sprinkle over the soup, giving it a gentle stir to distribute the herbs evenly.
Let the soup rest off the heat for 5 minutes, allowing flavors to meld. Then, ladle into bowls, garnish with more herbs if desired, and serve hot.
