The board shall appoint a director to serve at its pleasure who shall be the administrative head of the department. The director must carry out the policies of the board and administer the affairs of the department. The director may exercise all powers belonging to the board within the guidelines and policies established by the board. The director shall manage the administration and organization of the department and may appoint such assistants or deputies as the director considers necessary. The director may hire such employees as the director considers necessary for the proper administration of the affairs of the department. The director must prescribe the duties, powers, and functions of all assistants, deputies, and employees of the department.