Makinging the index.html the primary page

How do you build your wordpress site so that the site is not completely public before you have it tweaked and ready?

On a html site I use the index.html page as my primary home page and do not put any links on it until my site fixed up like I want it. Example:
https://www.wcgaragedoor.com/index.html

With the word press if a person goes to the primary domain name it takes them to the php (wordpress) website that I am not ready for all to see: https://www.wcgaragedoor.com

Is there a small snipit of code I can add to a wordpress file that I can remove later when I am ready for the site to be seen?

I want a back door so to speak so the site can be on the web and my client can view the site before it is public.

Thank you for any help you can give me.