You can create a separate pool for storing VMs that would be LUKS-encrypted and have your sensitive qubes there.
Note that unless you share your PC with someone else (and even then) this won’t do much, as your whole disk should already have been LUKS-encrypted by the Qubes installer.
I have an encrypted setup, but I would like to specially encrypt certain qubes so that if someone other than me tries to access them, they won’t open and can’t be hacked because they’re encrypted. How can I create a separate pool for the encrypted qubes?