Build a 404 page with Rey
In Rey there’s a simple feature that adds the ability to pick a Generic Global Section built with Elementor and show it on 404 pages.
Simply access Rey theme > Global sections in the backend and create a new generic global section in which you can add pretty much anything you need to.
You can access Customizer > General > 404 Page Settings and pick the newly created global section eg: https://d.pr/i/OSOdzQ .
Build with Elementor PRO
In case you’re running Elementor PRO, there’s even more flexibility with its Theme Builder which allows building these kinds of pages. More about how to create 404 pages with Elementor PRO .