Add Custom Widget Area

function custom_widget_area() {
    register_sidebar(array(
        'name' => 'Custom Sidebar',
        'id' => 'custom-sidebar',
        'description' => 'This is a custom widget area',
        'before_widget' => '<div class="widget-item">',
        'after_widget' => '</div>',
        'before_title' => '<h3 class="widget-title">',
        'after_title' => '</h3>'
    ));
}
add_action('widgets_init', 'custom_widget_area');