Delicious is signed a bit like favorite or taste, and that makes sense, doesn't it?
To sign delicious, take your open five hand, then touch your middle finger and your thumb together at your chin. As you pull your hand away from your chin, slide your thumb down from and at an angle to your middle finger (kind of how you snap your fingers, but do the motion for 'delicious' gently and with no snapping sound).
Teach your baby or toddler the delicious sign when you see a look of delight on them as they take a bite of their favorite food or a sip of their favorite juice or milk.
This is a useful flash card taught best in conjunction with your child's favorite food and drink flash cards. Children are a lot happier and less fussy when they can freely express what they would like to eat or snack on.