Mold assemblies for compression molding of footwear components include molds, heating elements, conductor plates, insulating layers and carrier trays. An upper mold assembly is placed into a fixture attached to an upper press platen. A lower mold assembly slides into and out of a fixture attached to a lower press platen. Heating elements within the mold assemblies connect to electrical contacts in the fixtures when the mold assemblies are installed in the fixtures, thereby providing electrical power to the heating elements and heating the molds. A conveyor is positioned to receive a mold assembly from (or transfer a mold assembly to) the lower press platen fixture when the lower platen is in a lowered position.