I prefer to add the wire on the bottom and use the tray under the crate to catch poops during 'hospital' stays.
If you do use the tray as a 'lid' make sure you secure it so it doesn't get knocked off.
I've found the foldable 24"L x 18"W x 21"H to be good.
2 doors are very handy.
Add 1x2" wire to the bottom, tight so it will still fold.
https://www.backyardchickens.com/articles/foldable-wire-dog-crates-a-good-tool-for-every-chickeneer.72619/