You are dealing with living animals so nobody can give you anything that will work 100% of the time. A lot of things can possibly help but they don’t come with guarantees.
I keep a golf ball in each nest all the time. I had a golf ball get scratched out of the nest onto the ground and a hen that normally laid in the nest laid next to that golf ball. When I moved the golf ball back to the nest and raised the lip a bit so it was harder to scratch out, that hen went back to laying in the nest. I’m convinced they help.
It’s not unusual for a pullet just learning to lay to drop an egg about anywhere, from the roost or on the ground in the coop or run. Most seem to have control from the start, but some can take a week or two to learn control. I don’t consider a pullet just starting to lay dropping a random egg somewhere to be a big deal.
When it becomes a problem is when it is not random but planned. Even with the golf balls in the nests and other hens laying in those nests, some hens will purposely make a nest on the floor. It may be a hidden place that she thinks is safe or even just shadows on the floor. If she regularly lays in a specific place and it is hollowed out a bit like a nest, she’s learned to lay there. It’s possible she will eventually move to a nest but not likely.
I’ve heard of people making a portable nest, maybe out of a cat litter box or something like that, and put it where she is laying. Once she gets to laying in it, gradually move it toward the nests a bit each day. When you get to the regular nests, either get rid of it and see if she switches or just leave it there.
Something that has worked for me. I built some of my nests so I could lock a hen in there if I wanted to. When I see her settling in her nest on the floor to lay, I catch her and lock her in a real nest until she lays. Usually this takes about a half hour and only once, but I had a hen that took over 3 hours to lay her egg in that nest and I had to do it again the next day. She did learn that second time.
Good luck! You may be at a stage this is not a big deal or you may have some work to do.