[Zope-CMF] rmoving right and left slots on login_form

[david convent]

hi there, here comes another newbie question :

my instance of plone portal (zope262/plone105) is a private protal, 
letting acces only to registered members.
I have defined other slots than the standard ones, and those are called 
for display at the very first page : the login_form.
As those slots call non accessible methods for anonymous users, portal 
members have to register with zope first using the standard zope loggin 
window before beeing authorised to acces the login_form.

can anyone tell me how i could get rid of all side slots on that very 
first login_form page ?