Freezing things like Fettuccine Alfredo
The best way to freeze something is to do it fast.  Chill the food first in the refrigerator before putting it in the freezer.  Keeping the food thin/flat rather than thick will help the center to chill faster. Loading up a sheet pan with individual portions works well for this - just be sure you have room for it in the refrigerator and freezer.

However, the larger problem with this type of sauce is re-heating of it - the sauce tends to split into its constituent ingredients.  Reheating the sauce very slowly on low heat is the best way to prevent the splitting.  You can also consider adding some lecithin to the sauce during cooking, which will help stabilize it.  See How can I reheat a roux-based (alfredo) sauce in the microwave without separation? and Keeping A Sauce From Separating for details.