This demo site page shows how to use Site Search 360's Smart 404 feature while displaying search results in embed mode. View the to check the configuration.

window.ss360Config = {
   siteId: '', /* Replace with your site id */
   searchBox: {
      selector: '#searchBox' /* Replace with the css selector of your search box */
   results: {
      embedConfig: {
         contentBlock: '.example__page-content-block'  /* Replace with the css selector of the DOM element you want to use */
   smart404: {
      caption: 'We couldn\'t find what you were looking for but these results might help',
      identifier: 'page not found',
      resultSelector: '#ss360-404',