Heyyo,
ok, there's 2 ways I believe. 1st the manual way:
start the server with mp_autoteambalance 0
.. or whatever that command is.
and then, add bots to the desired team you want. Simple.
Another way, more "on-the-fly" is with that metamod plugin that PMB made.. forgot the name, but check his site:
http://racc.bots-united.com
I think it's called the swapteams plugin. It has a command you can execute that sets it up as players vs bots I think, or at least whips players all onto the same team. (Am I using it wrong???
)