How Superhuman put the wall of love on its own page?

Unlike having a wall of love from a link, Superhuman added its wall of love to its own webpage, just like this 👇
notion image
It seems like a lot of coding and other work, but it just needs one line of HTML. You can do it too!
notion image
How you can do the same?
1. Create a new blank page
2. Paste the <iframe> code below to the custom code editor (* if available)
<iframe src='{use your space ID}/all' style='width:100vw; height:100vh; border:0;' />
Remember to put your own Testimonial space ID in the above code snippet. Here is a quick demo for Superhuman.