According to SLA By-Laws:

Election of the Executive Board and Members-at-large occurs at the Annual Meeting (usually in April). 

The board will issue a call for nominations to all neighbors at least a month before the Annual Meeting. The Scribe will place the names of those who are nominated and agree to serve on the slate. The slate will be circulated at least two weeks prior to the Annual Meeting.

Officer members will be elected by a vote of neighbors at the Annual Meeting, or by an online vote following the meeting.  The nominee who receives a majority of votes will win. In an election between more than two nominees, a candidate with a plurality of votes will win.

Board members will be elected to three-year terms. Typically, four board members will be elected annually. Members may be reelected.  

Any vacancy on the board can be filled by majority vote of the officers. A member appointed to fill a vacancy will serve the remainder of the unexpired term and until their successor is elected or appointed.