How to preview a wordpress site on a temporary/preview URL?

Hi there,

I’ve seen this question being posted quite often but I haven’t found one of them answered with a helpful (enhough) answer so here it goes:

I once in while build a new wordpress site for someone who already has a website and domain.

I want to be able to create a fully functioning WordPress site without the orginal domainname refering to it. The idea is that the customer can check out the new site and if OK, we can change the DNS settings.

I use plesk so I can use their Website Preview service but that gives me a semi/non-working website without CSS and access to, for example, the wp-admin site.

What is the easiest way with the least effort to create and fill a wordpress site under a temporary URL to take it in production later with the final URL?