Linked from: https://support.boldcommerce.com/hc/en-us/articles/208002516-Product-Options-1-0-Install-Instructions

shappify-options.liquid

<div style='display:none' id='shappify_custom_options_{{ product.id }}'></div><script async  src="//secure.apps.shappify.com/apps/options/generate_options.php?shop={{shop.permanent_domain}}&product_id={{ product.id }}"></script>
<script>
  $(window).load(function(){
    if(typeof shappify_options_{{product.id}} !== "undefined"){
      if(pojQuery("#shappify_custom_options_{{product.id}}").html() == ""){
                shappify_options_{{product.id}}();
      }
    }
});
</script>