Should I use a bare domain or a subdomain?

A bare domain is the domain itself, like yourstudio.com. A subdomain has something in front, like book.yourstudio.com.

A subdomain works with every DNS provider, so it is the safest choice. A bare domain works with some providers, including Cloudflare, Namecheap, Porkbun and DNSimple. GoDaddy doesn't support a bare domain for this, so with GoDaddy use a subdomain such as book.yourdomain.com. The Domain screen shows the exact records for the provider you pick.