To a 6-quart slow cooker, add onion, celery, and carrots. Then top with chicken, sprinkle the garlic, thyme, rosemary, and season with salt and pepper.
Pour the chicken stock all over the chicken, give everything a quick stir, and cover with a lid. Cook on LOW for 5-6 hours or on High for 2-3 hours.
When the chicken is done (internal temp is 165°F/74°C), remove it from the slow cooker and shred and set aside. Discard the bay leaves.
Add noodles and make sure they’re fully submerged in the liquid, cover with the lid, and cook for 10-15 minutes but be careful not to overcook them.
Taste and adjust the salt and pepper if needed, then return the chicken back in along with chopped parsley. Give everything a gentle stir and serve immediately.