From the Secret of Mary
Mary is called by St Augustine, and is indeed, the “living mold of God” . In her alone the God-man was formed in his human nature without losing any feature of the Godhead. In her alone, by the grace of Jesus Christ, man is made godlike as far as human nature is capable of it. A sculptor can make a statue or a life-like model in two ways:
By using his skill, strength, experience and good tools to produce a statue out of hard, shapeless matter; or by making a cast of it in a mold. The first way [the chisel] is long and involved and open to all sorts of accidents. It only needs a faulty stroke of the chisel or hammer to ruin the whole work. The second [a mold] is quick, easy, straightforward, almost effortless and inexpensive, but the mold must be perfect and true to life and the material must be easy to handle and offer no resistance.
Mary is the great mold of God, fashioned by the Holy Spirit to give human nature to a Man who is God by the hypostatic union, and to fashion through grace men who are like to God.
… Let us not imagine, then, as some misguided teachers do, that Mary being simply a creature would be a hindrance to union with the Creator. Far from it, for it is no longer Mary who lives but Jesus Christ himself, God alone, who lives in her.
-from Ch. 2, The Secret of Mary.