<script async src="https://shrd.co/embed/loader.js?id=cmseolafz000m04jpns5bxcxd&view=card&click=overlay&w=640&h=360&overlay=title%2Cdescription%2Cauthor%2CitemCount%2Cdate"></script>
One tag, no iframe. Survives WordPress, Squarespace, Wix, Webflow, any CMS that allows a <script> tag.
The script renders the collection block directly into the page at its own location. Updates to the teaser design ship instantly to every embed without you touching this code.