Adding Widget Ready Sidebar in WordPress Themes

// Register Sidebars
function custom_sidebars() {
 
    $args = array(
        'id'            => 'custom_sidebar',
        'name'          => __( 'Custom Widget Area', 'text_domain' ),
        'description'   => __( 'A custom widget area', 'text_domain' ),
        'before_title'  => '<h3 class="widget-title">',
        'after_title'   => '</h3>',
        'before_widget' => '<aside id="%1$s" class="widget %2$s">',
        'after_widget'  => '</aside>',
    );
    register_sidebar( $args );
 
}
add_action( 'widgets_init', 'custom_sidebars' );

To display this sidebar or widget ready area in your theme add this code:

<?php if ( !function_exists('dynamic_sidebar') || !dynamic_sidebar('custom_sidebar') ) : ?>
<!–Default sidebar info goes here–>
<?php endif; ?>