Lemony Chicken and Orzo Soup

INGREDIENTS

• Kosher salt, freshly ground pepper
• Lemon halves (for serving)
• 1 medium leek, white and pale-green parts only, halved lengthwise, sliced crosswise 1/2" thick
• 1 celery stalk, sliced crosswise 1/2" thick
• 1/4 cup chopped fresh dill
• 1/2 cup orzo
• 12 ounces skinless, boneless chicken thighs
• 1 tablespoon olive oil
• 6 cups low-sodium chicken broth