A flexible manifold adapted for use on a plate-fin heat exchanger core, the flexible manifold comprising a plurality of individual layers, each individual layer defining a lower floor, an upper floor, and two side walls. Each of the plurality of individual layers is adapted to channel a flow of a medium therethrough, each of the plurality of individual layers includes a plurality of vertical members, each of the plurality of vertical members extends vertically from the lower floor to the upper floor of the respective individual layer, and each of the plurality of vertical members is configured to provide structural support for the respective individual layer. The vertical members can be vertical guide vanes and/or vertical columns having a round and/or hydrofoil cross-sectional shape.