is it possible to create slave site automatically via a script or form?

You have the possibility to create website from the front-end.
Once you have prepared the rule in a JMS Templates, you can use it several times to create the website.

There is no "batch script" available.
If you want to create a huge number of slave site (several hundreds or thousand of slave site) in a very short time, we have an internal component that allow import a tabulated file to build the websites described in the tabulated file. This is not a product because we know that there are bugs due to timeout of the servers. So you have to run it several time.
Perhaps we will do a product in the future.