Cloudflare

1. Open the zone in Cloudflare and go to DNS → Records → Add record.
2. Type CNAME, Name go (or the subdomain you chose), Target: the edge host shown in Anchorpost.
3. Set Proxy status to DNS only (the cloud icon turns grey). This is required: with the orange cloud Cloudflare hides the record and SSL cannot be issued.
4. Save, then check Domains in Anchorpost. It usually turns Active within a minute.

If the domain is still Pending after a while, the most common cause is the orange cloud.