BookStack/app/Config/view.php

<?php

/**
 * View configuration options.
 *
 * Changes to these config files are not supported by BookStack and may break upon updates.
 * Configuration should be altered via the `.env` file or environment variables.
 * Do not edit this file unless you're happy to maintain any changes yourself.
 */

// Join up possible view locations
$viewPaths = [realpath(base_path('resources/views'))];
if ($theme = env('APP_THEME', false)) {
    array_unshift($viewPaths, base_path('themes/' . $theme));
}

return [

    // App theme
    // This option defines the theme to use for the application. When a theme
    // is set there must be a `themes/<theme_name>` folder to hold the
    // custom theme overrides.
    'theme' => env('APP_THEME', false),

    // View Storage Paths
    // Most templating systems load templates from disk. Here you may specify
    // an array of paths that should be checked for your views. Of course
    // the usual Laravel view path has already been registered for you.
    'paths' => $viewPaths,

    // Compiled View Path
    // This option determines where all the compiled Blade templates will be
    // stored for your application. Typically, this is within the storage
    // directory. However, as usual, you are free to change this value.
    'compiled' => realpath(storage_path('framework/views')),

];