Add the diced carrots, celery, onion, and minced garlic to the slow cooker.
Place the boneless skinless chicken breasts on top of the vegetables in the slow cooker.
Pour the chicken broth over the chicken and vegetables.
Add the dried thyme, dried oregano, black pepper, and salt to the slow cooker.
Cover and cook on low for 4 hours.
Remove the chicken breasts from the slow cooker and place on a cutting board.
Add the orzo pasta to the slow cooker and stir well.
Shred the chicken breasts using two forks and return the shredded chicken to the slow cooker.
Cover and cook on high for an additional 30 minutes, or until the orzo is tender.
Stir in the olive oil, lemon juice, and chopped fresh parsley.
Taste and adjust seasoning with additional salt and pepper if desired.
Serve hot.