I'm no UNIX Guru, but I've had to set up a handful of slices for various web projects. I've used the articles on there to set up users, a basic firewall, nginx or apache, and other bits and pieces of a basic web server.
I foresee more slice administration in my future. Is there a more efficient way to set up users, permissions, and software on a clean slice than configuration by hand?
Depending on the number of machines you might find it makes sense to use something like CFEngine, or Puppet, to configure the new installs.
That brings your work down to configuring each new machine as a CFEngine, for example, client. Then that may be used to install the packages, edit files, & etc.
There are a few articles I wrote on the subject, with a Debian bias, here:
It sounds like you can create a new slice from the backup of an existing one. This might not work for you if the slices would be different sizes, different distros, etc. Their forums mention this: Clone a slice?