You can put a bed or blankets in the bottom to make it a bit more comfortable, as the hard plastic bottom won't be very comfy for your pooch to sleep on. (topdogtips.com)
The roomy bag has reinforced handles and a removable plastic bottom insert for easy cleaning. (parrishkauai.com)
I bought the cages that the pet store suggested plastic bottom and wire sides and top. (caringpets.org)