On the Laravel News site they've posted a quick tutorial showing how to add in "maintenance mode" management functionality into Laravel Nova, the recently released administration panel product for Laravel-based applications.
If for some reason you've been on another planet (see what I did there?), Laravel Nova is Now Available and the community has been rather busy building open-source tools around Nova.
One of those open-source tools is by David Piesse, who created a Laravel Nova extension that allows you to manage the maintenance mode of your application from Nova
The package to add the functionality is easily installed via Composer and integrate via a service provider. This then adds a new toggle to the administration panel's UI to enable or disable maintenance mode (as well as an icon showing the current status).