01 - Heat olive oil in a large soup pot over medium heat. Add diced onion, sliced carrots, and celery. Sauté for 5 minutes until vegetables begin to soften and become fragrant.
02 - Stir minced garlic into the vegetable mixture and cook for 1 minute, stirring constantly to prevent browning or burning.
03 - Add chicken pieces to the pot and cook, stirring occasionally, until lightly browned on all sides, approximately 3 to 4 minutes.
04 - Pour in chicken broth. Add oregano, thyme, basil, bay leaf, red pepper flakes, salt, and black pepper. Bring mixture to a gentle boil, stirring to combine seasonings.
05 - Reduce heat to low, cover pot, and simmer for 15 minutes until chicken is fully cooked through and vegetables are tender.
06 - Stir in chopped spinach, lemon juice, and lemon zest. Simmer uncovered for 2 to 3 minutes, just until spinach wilts completely.
07 - Remove pot from heat. Discard bay leaf. Stir in fresh parsley. Taste and adjust salt and pepper seasoning as needed.
08 - Ladle hot soup into serving bowls. Garnish with additional fresh parsley and a squeeze of fresh lemon juice if desired.