The board of commissioners shall be elected by the members of the Idaho State Bar who are eligible to vote in the election and who shall vote by ballot. The candidate from any division receiving the greatest number of votes of that division shall thereby be elected commissioner from such division. Only residents of or members of the Idaho State Bar maintaining an office in a division may vote for candidates for commissioner of that division. The ballots shall be deposited in person or by mail with the executive director of the board, or such other officer as it may designate. There shall be an annual election by the members of the Idaho State Bar eligible to vote for the purpose of electing successors to the commissioners whose terms expire. A commissioner shall be elected during 1974 and every third year thereafter from each of the northern and central divisions; during 1975 and every third year thereafter from each [of] the western and central divisions; and during 1976 and every third year thereafter from the eastern division. The board shall fix the time for holding the annual election and prescribe rules and regulations in regard thereto not in conflict with the provisions of this act. The board shall, in accordance with its rules, give at least sixty (60) days’ notice by mail of the time for holding the election each year. In the event a vacancy shall occur on said board otherwise than by expiration of the term of a commissioner, such vacancy shall be filled by appointment by the remaining members of said board. Such vacancy shall be so filled from the members of the bar residing, or maintaining an office from which they primarily practice law in the state of Idaho in the division where such vacancy occurs and who have appointed an agent for service of process within the state.