It took the champions-elect only 16 minutes to break the deadlock when Stearman found himself unmarked at the far post to head home a corner following a flick-on from Danny Batth.
Orient had a penalty appeal for handball by Stearman turned down before the visitors doubled their advantage on 33 minutes when O's defender Matthieu Baudry carelessly gave the ball away and Sako fired into the corner of the net.
Ikeme then produced saves to deny Mooney and Cox and was grateful to his crossbar for keeping out a Shaun Batt effort.
However, substitute James Henry put the issue beyond doubt in stoppage time when he fired home from 25 yards.
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