(1) All assistants, deputies, and other subordinate officers whose appointments are not otherwise provided for must be appointed by the officer or body to whom they are respectively subordinate.
(2) When the number of such deputies or subordinate officers is not fixed by law, it is limited only by the discretion of the appointing power.
(3) The appointment of deputies not otherwise provided for must be made in writing filed in the office of the appointing power or the office of its clerk.