You are putting them in the van, or you possibly will? I don't want to grill you or anything, surly you have a lot to transport, and only so much room. You serisouly need so consider being 100% certain they will be in the van though.
Chickens hate change, I once re homed 3 hens that had to travel for an hour and a half in the back of a truck. They were in a plastic dog crate that as stationed right up against the back of the truck as a wind block though, so they were just fine.
That is MUCH to far for those hens to be comfortable, or even possibly survive in the back of a truck. If you love them like children, you will find a way to get them in the van, because if you had children, would it be safe to strap them on the flat bed trailer, cover then in a trap because you wanted to fill the seats with supplies? No.
Again, sorry if I sound harsh or rough, I don't mean to, just trying to paint a picture of how important it is that you get them in the van, its important.
Otherwise, I bet you could use straw for the base of the crate. That will stay in there better and be comfortable for them. Straw or an old towel would probably work to. Something they can scratch up would be nice though, as thats familiar to them. Safe travels.