Install a new website before setting the domain?

Hi,

I have a hosting plans with multi website and want to add a new website on it
but with a foreign domain.

So my idea was :
- Add a new website on my multi website hosting (with my foreign domain name)
- Put the files of the website in the folder on the OVH server
- Check if everything is ok from my computer (i set my hosts file to use the OVH server and then check if everything is ok on the website)
- If everything is ok, ask to the owner of the domain to edit the DNS zone with the new IP to use the new OVH server.

Problem : It looks impossible to install a website without editing the DNS zone first ?
Source : https://docs.ovh.com/gb/en/hosting/multisites-configuring-multiple-websites/#add-external-domain

How can i do this ?

Thanks