You can skip prevalidation, just do cname + http validation, they just add cname and wait. Would incur more downtime compared to prevalidation though if they were already using the domain.

Otherwise, Business or higher can be used with CNAME setups, you add their base simonilincev.com as a cname biz or higher partial zone, and then for each subdomain they want to use, you have them cname to a specific cloudflare.net subdomain and configure the record on their end