On the first Monday of January following the municipal election, members of the board shall assemble at a designated meeting place and shall organize by electing one of their own members as chairman. This member shall preside at all meetings and perform other duties as the board may prescribe. In the absence of the chairman, the board shall elect a temporary presiding officer. The board shall adopt rules for its procedure and conduct of business. Any vacancy shall be filled by an elector from the municipalities involved appointed by the remaining members of the board.