Pour out approximately 1 cup of milk from the gallon container so that the container does not break when the milk expands as it freezes.
Seal the container tightly and place in the freezer standing up right.
Thaw in the refrigerator (not at room temperature) when ready to use. The milk will likely separate when it freezes, so shake thoroughly once it thaws to incorporate the ingredients back together.
Notes
Milk can be stored in the freezer for up to 6 months.