Set a new DispVM base?

How do I set a base for the VM. I have a debian and a whonix disposable vm but I’m guessing this is something else? I am having trouble setting up a Qubes builder VM and this is what I pulled from journalctl:

Mar 14 18:24:30 dom0 qrexec-policy-daemon[2455]: qrexec: qubes.VMShell+WaitForSession: builder1 -> @dispvm: denied: policy define 'allow' action to @dispvm at /etc/qubes/policy.d/90-default.policy:94 but no DispVM base is set for this VM

Maybe it is referring to the Qubes builder VM’s Settings > Advanced > “Default disposable template”