WP register sidebar (widget area)
register_sidebar(array(
'name' => __('Sidebar Name'),
'id' => 'sidebar-custom-id',
'description' => __('Custom Widget area'),
'before_widget' => '<div class="sidebar-custom-class">',
'after_widget' => '</div>',
'before_title' => '<h2>',
'after_title' => '</h2>',
));