Sorry but I have no account in all the possible Hosting company.
The material that is provided concerning the hosting configuration comes from customers that have provide the material for a documentation.
Try to review the tutorial step 0 for the concept and the FAQ on hosting server.
www.jms2win.com/component/faq2win/?view=category&id=12
Perhaps you will find something similar for the DirectAdmin.
When I have a look to the DirectAdmin demo websites, if the Symbolic Link is forbidden, you can try define a CNAME record in the DNS configuration that will result by creating an alias on the domain.
Perhaps you will have also to use the "Domain Pointer" to create alias on an existing websites.
When creating a sub-domain in DirectAdmin, this create a sub-directory on your website.
You have to check if the Symbolic Links is allowed.
If YES, you can deploy the slave site into this directory.
See DirectAdmin help
www.site-helper.com/subdomains.html