I've followed Facebook's Tag API guide to create "Custom Audiences" by using "Custom Events": https://developers.facebook.com/docs/ads-for-websites/tag-api#remarketing
The final code reads:
!function(f,b,e,v,n,t,s){if(f.fbq)return;n=f.fbq=function(){n.callMethod?n.callMethod.apply(n,arguments):n.queue.push(arguments)};if(!f._fbq)f._fbq=n;n.push=n;n.loaded=!0;n.version='2.0';n.queue=[];t=b.createElement(e);t.async=!0;t.src=v;s=b.getElementsByTagName(e)[0];s.parentNode.insertBefore(t,s)}(window,document,'script','//connect.facebook.net/en_US/fbevents.js');
fbq('init', 1234567890); //Of course, I'm using my own Pixel ID ;)
fbq('track', 'PageView');
fbq('trackCustom', 'Facebook Test Audience');
The above code seems to work just fine and the custom event is being triggered (GET requests are sent and cookies "datr" + "fr" + "lu" set).
However, I cannot find "Facebook Test Audience" in the Ads Manager in order to advertise to it.
Does it take time to finally show up?
Any other ideas?