Combine the carrots, celery, onion, garlic, thyme, rosemary, and bay leaf in a slow cooker. Arrange the chicken on top of the vegetables. Season with salt and pepper to taste.
Pour in the broth.
Cover and cook until the chicken and vegetables are tender, about 3-4 hours on LOW or 1 ½ - 2 hours on HIGH.
Remove the chicken to a cutting board.
With the slow cooker on the HIGH setting, stir in the noodles and cook until tender, about 22-27 minutes.
While the noodles cook, shred the chicken with two forks or dice into bite-size pieces. Tent with foil to keep warm.
Once the noodles are tender, stir the chicken back into the broth. Add the parsley and lemon juice (if desired). Taste and season with additional salt and pepper, if necessary.
Ladle into bowls and garnish with additional fresh herbs.