Place onion in a lightly greased 6-quart slow cooker; top with potatoes and carrots. Combine 3/4 teaspoon salt, 1/4 teaspoon pepper, broth, and next 3 ingredients. Pour broth mixture over vegetables. Combine paprika, remaining 1/2 teaspoon salt, and remaining 1/4 teaspoon pepper; rub evenly over chicken thighs, and arrange on top of vegetables.
Cover and cook on LOW 8 hours or until chicken and vegetables are tender. Garnish, if desired.