To sign spoon, make a bowl by cupping your non-dominant hand and a spoon with the index and middle fingers of your dominant hand. Spoon invisible contents up a short distance from the "bowl," without bringing your hand to the mouth. (Note that when you bring the fingers to your mouth, you are already signing soup).
We use spoon with babies under one when we are teaching them how to eat on their own.
We can teach our babies to sign spoon in association with meals. Using the spoon is a great skill for babies under one year of age.