It’s easier to just lay down a skirt on top of the ground. You want the hardware cloth along the bottom edges of your enclosure at least. I just have 2x4 fencing on the floors of my rabbit tractors and nobody has tried to get through that.
Theoretically, a bunny small enough to squeeze through the 2x4 openings *could* burrow out, but I haven’t had a problem with that at all. You could bend hardware cloth out onto the floor for several inches, and up the wall for as high as you think necessary—a couple feet, at least. I personally wouldn’t bother with a very wide HC skirt on the floor, but I *would* use the 2x4 wire on the floor for at least several feet in from the perimeter fence.
Depending on how big the enclosure is, you may not need wire across the whole floor—just close to the perimeter. Someone else will likely have more info on that, or you could just go with your gut.