I've had Google Workspaces/Gsuite like that, but how do you accomplish the same thing with just gmail? Do you have a separate email service forward to it, or is

I've had Google Workspaces/Gsuite like that, but how do you accomplish the same thing with just gmail? Do you have a separate email service forward to it, or is there some way to set gmail as your DNS MX mail server and have it direct a custom domain into (and out of?) your gmail address?