I think the current easiest and best way is to:

1. Install Drupal 8 with the recommended composer template

   composer create-project drupal/recommended-project my_site_name_dir

2. Add CiviCRM:

   composer require civicrm/civicrm-asset-plugin civicrm/civicrm-drupal-8 civicrm/civicrm-packages

3. Enable CiviCRM in the modules list

I think the current easiest and best way is to:

1. Install Drupal 8 with the recommended composer template

   composer create-project drupal/recommended-project my_site_name_dir

2. Add CiviCRM:

   cd my_site_name_dir
   composer require civicrm/civicrm-asset-plugin:^5.25 civicrm/civicrm-drupal-8:^5.25 civicrm/civicrm-packages:^5.25

3. Enable CiviCRM in the modules list