Best Way to Add to Mailing List from an Email (sign up forms don't embed in email well)

I am trying to create a new mailing list (call it mailing list B) which will be a subset of all of our subscribers. We want to use this mailing list to send content to specific subscribers.

I want to send out an email using campaigns to all of our users that fit a particular criteria (this I know how to do, call it mailing list A) but I want them to have something they can click on in that email that will add them to mailing list A.

Here is how we are currently doing it:

Put a google form in the email
Export from the google form to update zoho crm
Sync the list from CRM to campaigns mailing list A
Send to mailing list A

This involves a manual step so I'd like to get away from this process.

Another idea I had was to house the signup form on one of our own pages then link to it. This would require us setting up a new sign up form page each time we want to do this again (which will end up being a lot). Is this the only way to do this or is there something I'm missing?