Developing one theme while keeping other live

Hi,

My current site runs on wordpress, but I am looking to create a new theme for the site. I’ve made a few themes before, but have only done them for brand new sites.

What is the best way to go about things so that my current site remains undisturbed and viewable by the public, but so I can work on a new theme using the same database in the background?

Tried searching but didnt have much luck

Thanks