According to this article What’s new with Cloudflare for SaaS? a pair of IP addresses can be used for domains where you want to use the Apex Hostname for a custom domain.
For our SaaS customers who want to allow their customers to proxy their apex to their zone, regardless of which DNS provider they are using, we give them the option of Apex Proxying. Apex Proxying is an SSL for SaaS feature that gives SaaS providers a pair of IP addresses to provide to their customers when CNAME records do not work for them.
Cloudflare starts by allocating a dedicated set of IPs for the SaaS provider. The SaaS provider then gives their customers these IPs that they can add as A or AAAA DNS records, allowing them to proxy traffic directly from the apex of their zone.
I cannot find where these IP addresses are. Is someone able to point me in the right direction?