It needed to be big and talk. So once again I go to my old standby; foam, and piping...
Step 1: The frame of the head
When operating a puppet, even on a large scale, the more direct interaction with the puppet the better. This puppet is made to be held in one hand while the other hand operates the jaw.
The foam allows the head to be huge but lightweight. The frame for the head doesn't have to be as reinforced as say, that of Audrey II, because it is not under as much strain due to movement or direct physical interactions with the actors.