Whats the BEST way to furnish (set up) my dogs crate for when he flies on the plane? so hes comforable?

its going to be a LONG flight (12 hours) to japan. and i cant imagine being stuck in a small kennel barely able to move around. so i really want to make it roomy and comfortable for my dog. How should i set up the floor of the kennel? so when he pees/poos he wont have to step all in it and it wont be all that messy?