This creates a new directory and populates it with files that let it be used as a buildslave's base directory. You must provide several arguments, which are used to create the initial buildbot.tac file.
The -r option is advisable here, just like for create-master.
buildslave create-slave -r BASEDIR MASTERHOST:PORT SLAVENAME PASSWORD
The create-slave options are described in See Buildslave Options.