You need an active url to build a working wordpress website. So, you can do this by two method.
Method One:
1) Create an account on any working sub-domain name. Like say domain.com is working on your server. So, create a new account on any sub-domain like dev.domain.com
2) Now start building your Wordpress website on dev.domain.com
3) Once your website is ready, change domain name of this account from WHM.
4) Change domain name in WordPress database from Phpmyadmin
Changing The Site URL « WordPress Codex
5) Update nameserver of your domain name from domain control panel at your registrar.
Method 2
This is most preferred method.
1) Install any local server like wampserver / xampp on your computer. Simple installation, will take hardly 5-10 minutes.
2) Install Wordpress on your computer.
3) Develop your wordpress website on your local server.
4) When website is ready, create an account on your server.
5) Change nameserver of your domain name.
6) Transfer website from local computer to server using Wordpress export / import feature.
Done!!!