Sauté fennel, onion, and carrots, approximately 5 minutes.
Add garlic, sauté until aromatic, approximately 1 minute.
Combine chicken broth, bay leaves, thyme, oregano, dill, salt, and black pepper in a large soup pot; bring to a boil over high heat.
Add orzo and return to a boil. Reduce heat to low and simmer, partially covered, until orzo and vegetables are tender, 8 to 10 minutes.
Stir in chicken and cook until heated through, about 5 minutes.
Off heat, stir in lemon juice and fennel fronds.
