I unchecked all the security boxes, but employees still have access

You may have unchecked too many boxes.  The first column is Require Access.  This controls whether a password is required to access a section.  If that is unchecked, the employees will have access to that section even if their security profile does not have access to it.

In the example below, no security profile has the ability to close the SalonTouch program.  However, because the Require Access is marked as False, no password is required and all profiles can close SalonTouch.