1. A holder for holding a biological sample container in a biological sample processing apparatus, the holder comprising: a vacuum bed having a planar surface for receiving a lower surface of a biological sample container; a perimeter portion comprising a seal surrounding the vacuum bed, the seal being dimensioned to receive a lower perimeter edge of a biological sample container; and an exhaust outlet for evacuating a volume defined by the vacuum bed, the perimeter portion and a biological sample container received on the seal so that the lower surface of the biological sample container is flattened against the planar surface of the vacuum bed.