Mini coop - needs a floor?

I have a custom-built chicken coop and run for my flock that has worked well, but I’m adding a “halfway house” to my porch. This setup will be used for new/younger chickens before introducing them to the flock, sick chickens, bullies, etc. I like the size of this store-bought coop (and already committed, it’s ordered!), but what can I add to the bottom of it to give it a floor?

My porch is eh. There are cracks and I feel like the run/coop needs a floor that is not the wooden porch. Any suggestions?