Add page slug to body class

functions.php

<?php

function custom_body_class($classes){	
	global $wp_query;
	if ( is_page() ) {
		$post_obj = $wp_query->get_queried_object();
		array_push($classes, 'slug-'.$post_obj->post_name);
	}

	return $classes;
}

add_filter('body_class', 'custom_body_class');