There is provided a molding stack assembly (202) for producing a molded article (214), the molded article (214) including a neck finish (218) which includes a support ledge (222), the molded article (214) suitable for subsequent blow-molding into a final shaped container. The molding stack assembly (202) comprises a core insert (204), a lock ring (206), a split mold insert (208), a cavity flange (209) and a cavity insert (210) for jointly defining, in use, a molding cavity (212) for forming the molded article (214), the split mold insert (208) and the cavity flange (209) defining a split line (226) therebetween, the split line (226) being defined substantially along a portion of the support ledge (222); a biasing member (230) disposed, in use, between the cavity flange (209) and the cavity insert (210), the biasing member (230) being configured to: (a) under applied clamp force, to allow the cavity flange (209) to abut the cavity insert (210); and (b) during initial stages of the mold operation to bias the cavity flange (209) away from the cavity insert (210).