I built a floor similar to a deck or porch. It gets them just high enough off the ground. Sometimes you can get lucky and find someone wanting to get rid of a old deck and you can just set your kennel on top of it
I'll take some pics of mine tomorrow and post. I built mine for $150-$200 I think but I already had the chain link and the tin was a freebie. I done it up nice. It works great if your dog usually airs in the kennel. It just washes right out or goes between the cracks. Also most of the time it is already pressure treated so it's gonna last a while.