Hi!! I’m so excited for you and your bunny!
We have a grid enclosure as well, and for Paisley I have used foam interlocking mats as flooring. I also put a fleece blanket or two on it and tie it to the corners so that it won’t move, and can absorb any accidents she has (which is rare now, thankfully) or any water spills and such. To protect our carpet I’ve just put plastic sheeting underneath the foam mats, but made sure Paisley could never get at it and it’s not visible.
When Paisley had her (accidental) litter, the babies would pee everywhere so I put some old towels underneath the fleece and that helped keep it from reaching the mats. These mats aren’t too expensive, and can usually be found at places like Walmart or Home Depot for about $15. Or, you could find some used ones and just wipe them off well, which is what I did
I find that this is nice and easy on their feet, which helps to prevent sore hocks.
Hope that helped!