FancyMenu allows you to customize existing GUI screens, but it also allows you to add completely new ones and fill it with elements.
To add a new screen, navigate to Customization -> Custom GUIs -> Manage Custom GUIs.
In the next menu, click on New GUI.
Here you need to give your new GUI a unique identifier and you can customize other parts of the basic screeen behavior.
When you're done, press Done.
Now you have a new empty GUI. To open it, select the GUI in the Manage Custom GUIs menu and click on Open GUI.
This will open the still pretty empty GUI screen. To make it less empty, just create a new layout for it like you would do with any other screen.
The last part is to give normal users access to your GUI. The easiest way to do that is to use the Open Screen or Custom GUI action with a button, slider or ticker.
You can also open your custom GUI via an in-game command.
This even allows you to remotely open the GUI for other users!