There doesn't seem to be a way to post without it having to be a reply to something earlier.
There are two white boxes at the bottom of a page down just below and to the left of Administrative, to the right is the Hop to box. They have written in them in odd flourished writing, "post topic" and "post reply". The post reply will post a reply that isn't referenced to a post. That seems to be discouraged though.
lfen