I believe that positive reinforcement is the best and most effective method. You can even try clicker training. I do agree with the others, I think you will have challenges training an unspayed female. It’s not impossible. I have seen it done, but nature/hormones create a strong drive to mark. But a rewards method is more effective. Have you ever tried clicker training?
How old is she? If she’s under a year, she may be in some strong hormonal stages
Do you have other animals where she roams?
Was she litter trained for a while and then stopped, or has her litter box behavior just changed recently?
How far outside of her litter box does she pee? Sometimes peeing right outside of the litter box can mean health issues like a UTI.
I know you said you are in a remote area — where is the nearest rabbit savvy vet? I know not everyone has decent access to a good rabbit-savvy vet. If you are not sure, check out this post that has several resources for finding vets in U.S. and world wide. https://binkybunny.com/FORUM/ta…fault.aspx
It is always good to find at least one somewhere because your bunny may need vet care one day. (even if you don’t spay). I don’t think any of us have ever had a rabbit that didn’t need to see a vet at least once. They are susceptible to serious, but treatable issues, by a good rabbit vet.
I’m glad you asked for advice before you used the cage as her time-out for litter training, because I also agree it could make it worse.