The bread must be a dinner roll from the meal as well.
If the sandwich or any similar food creation is created not on Thanksgiving Day or not following any of the specifications previously mentioned it is simply a Thanksgiving Sandwich, and NOT a Yum Yum Boat.
Person 1: Dude, I'm making a Yum Yum Boat
Person 2: It's the day after Thanksgiving, that's not a Yum Yum Boat, that's a Thanksgiving Sandwich!
Person 1: Damn!