Injection-molding processes and systems are described herein. An exemplary method involves: (a) holding one or more inserts in a desired position within a mold cavity by contacting a retractable core to at least a portion of each insert, wherein the retractable core is a feature of a mold plate; (b) while the one or more inserts are being held in the desired position by the retractable core, initiating an injection of molten plastic into the mold cavity; (c) retracting the retractable core from the one or more inserts while continuing the injection of molten plastic into the mold cavity, wherein retracting the retractable core creates additional cavity space within the mold cavity between the retractable core and the one or more inserts; and (d) continuing the injection of molten plastic into the mold cavity until the mold cavity, including the additional cavity space, is filled. The retractable core is preferably retracted at a point when molten plastic filling cavity space further from the retractable core has substantially cooled and hardened, while molten plastic filling cavity space in close proximity to the retractable core remains substantially heated.