Flow field plates in solid polymer electrolyte fuel cells can be subject to ice blockages in certain areas during freeze start-up, e.g. the backfeed ports and slots used in some flow field plate designs which connect an outlet plenum channel for a reactant to its outlet. By incorporating a similar and adjacent relief backfeed port, slot and plenum channel arrangement in which the relief plenum channel is separated from the outlet plenum channel by a landing, a relief outlet for the reactant is provided through the adjacent gas diffusion layer.