Add the sliced carrots, celery, diced onion, and minced garlic to a 6-quart crockpot.
Place the chicken breasts over the vegetables.
Pour the chicken broth into the crockpot. Add the dried thyme, rosemary, bay leaf, salt, and black pepper.
Cover and cook on LOW for 6–8 hours or HIGH for 3–4 hours, until the chicken is tender and reaches an internal temperature of 165°F (74°C).
Carefully remove the chicken from the crockpot and place it on a cutting board. Shred the chicken using two forks.
Remove and discard the bay leaf. Return the shredded chicken to the crockpot.
Add the egg noodles during the final 20–30 minutes of cooking. Cover and cook on HIGH until the noodles are tender.
Turn off the crockpot and stir in the fresh parsley and optional lemon juice.
Taste the soup and adjust the salt and black pepper as needed.
Ladle the crockpot chicken noodle soup into bowls and serve warm with crusty bread or crackers.