A little boy punching out flashcards from the cardboard they came in.
A boy holds some flashcards in his hands
In order to be punching out flashcards, the boy would have to use his hands to punch.
Punching out flashcards implies flashcards in his hands, and little boy is boy.
If a person is punching out flashcards from cardboard, he must be holding the cardboard and by extension holds the flashcards.