To set up the cloaking domain you first need to register an account in a 3rd party service called Postback. Email.
This service is used to generate email mailboxes on the fly, and will also help with automating the setup of all the DNS records required for configuring the Cloaker. Depending on the number of domains you are planning to use, you should choose the appropriate plan from Postback. Email, but for a simple setup one domain with a Single plan (10$) should be good enough to get you started.
Once you register an account in postback. email and activate your subscription, you will have 4 options for setting up a domain with their system
Purchase Domain - this is the recommended option.
In this option, you will need to choose a name or generate one randomly, and purchase it directly through PostBack.Email. The cost for the domain might be a bit more expensive but it will not be registered on your name on the domain provider, which is an advantage for additional anonymity.
Integrate with NameCheap via API - in this option you can put the API key of your NameCheap account (you will be asked to add some IP to the whitelist as well for the integration to work), and PostbackEmail will connect to your account and automatically import the domains that you have there.
Integrate with CloudFlare via API - in this option you can put the API key of your own CloudFlare account, and PostbackEmail will connect to your account and automatically import the domains that you have there.
Manual Setup - not recommended - experts only!
In this setup, you will not benefit from the automation that postback email provides and you will need to set up your DNS records manually. When you add the domain to FBAS you will need to configure the DNS records for the cloaker domain as well manually. Therefore this is highly not advised.
Once you have configured your domain(s) in postback.email, you will need to create an API key for PostbackEmail in the profile settings of your account, and use this API key inside FBAS on the popup that is opened when pressing the “Connect Domain” button on the Domains page.
Connect Domain in FBAS"
For connecting the domain, go to Domains in the left menu and click on connect domain.
Paste the API key of the postback email and click on connect domain. You can see the list of the domains you're having in the postback email.
You need to deploy a small server, it will take a little time to deploy the server.
once your server is deployed, select the domain and server & click on Import and Setup.
Your domain is all good to use for cloaking.
Please use the domain particularly for cloaking only, the domain which is for cloaking shouldn't be used for any other purposes.