How do I create a custom 404 page?
Possible Answers to Your Question:
404 pages are accessed dynamically, so you cannot just create a page called 404.
To customize it, you need to create a child theme, copy in the 404.php and customize its HTML structure. There are also some plugins like this one that help you do this if you do not have the coding skills to do template modifications.
May be the plugin “Easy 404 Redirect” will help you to redirect the 404 page to your custom layerswp page.