How to implement redirect to custom 404/403 pages? Hello Drupal community.  

What I am trying to do is if error 404 or 403 occurs it redirects to a custom page instead of showing standard error message.

I tried to write “/error/404” on the “Base site settings” page and created a content with the same alias but it didn’t work.
So when I try to access a page with some random url it still shows me a standard error message but not the content with “/error/404” alias.

Is my understanding of this functionality wrong? Should I try another approach?
This is build in to Drupal and the simple way to do this is to create separate pages for both error codes and add your own wording as necessary.

Then go to the error pages section of site settings at /admin/config/system/site-information and add the path of your custom error pages.