The fluxbox package in the repo first checks for any existing .fluxbox directory in /home/username. If it finds one, then it _doesn't_ add any custom configs so as to not overwrite any configurations a user may have had already.
So, since you created a .fluxox directory, the fluxbox package does not make any configs for you because it thinks you already have working ones.
Just remove .fluxbox from your home directory, and then as root run:
slapt-get --install fluxbox --reinstall
to reinstall the package. After the package reinstalls, you should see a new .fluxbox directory appear.
That should fix the problem you are having. This is for fluxbox 1.0RC3 btw.