Prep your celery and carrot. Trim any fat off the chicken.
Add all ingredients except for the salt & pepper, lemon juice, parsley, and orzo. Cook on low for 6-8 hours.
About 30 minutes prior to serving, remove the bay leaves, shred the chicken with 2 forks, and add the lemon juice, parsley, orzo, and salt & pepper. I recommend stirring every 10 minutes or so because the orzo may stick to the bottom of the slow cooker otherwise. Serve immediately.
You can also use boneless skinless chicken thighs if you prefer dark meat (I'd use 6 of them in this recipe and keep the cooking time the same). If you're cooking this for the full 8 hours the chicken breasts may dry out a bit - you may want to considering using chicken thighs instead.
If you're cooking it for 6 hours or less, I do suggest ensuring your chicken is properly cooked when you go to shred it.