You may be able to achieve what you want with some combination of the ‘has_archive’ and ‘rewrite’ arguments when registering your custom post type. Perhaps something like this:
'has_archive' => 'about/employees',
'rewrite' => array(
'slug' => 'about/employees',
)
Don’t forget to flush your permalink settings after making this change, and watch out for URL conflicts if you already have a page at /about/employees/.
