Proper Way to Load stylesheet on Condition

You’ll need to put the if statement around the line that enqueues in the first place.

// enqueue styles for child theme
function wowdental_enqueue_styles() {

    // enqueue parent styles
    wp_enqueue_style('Divi', get_template_directory_uri() .'/style.css', 
    get_the_time() );

    // Flip3d css
    // flip3d only on home page
    if( is_home()  ) {
        wp_enqueue_style( 'flip', get_stylesheet_directory_uri() . 
'/css/flip.css', get_the_time() );
    }


    }
add_action('wp_enqueue_scripts', 'wowdental_enqueue_styles');

To do it like you have it in the original code, you’d need to use wp_register_style first, then keep the enqueue in the if.