I want to create a Google Cloud Platform project via REST API.

But apparently I can’t get OAuth credentials without a first GCP project created, and I want to create a GCP project via REST without having to create another GCP project manually first.

You can create a project via REST via url:
https://cloud.google.com/resource-manager/reference/rest/v3/projects/create

In the “Try this method” side panel you can create a GCP project via API Explorer OAuth login.

It is possible to create a project there without creating a GCP project first.

The question is, how to create a GCP project like the API Explorer in the URL above?
How to get the OAuth credentials to do that?