add_action( 'carbon_fields_register_fields', 'crb_attach_home_options');

function crb_attach_home_options() {
  Container::make( 'post_meta', 'Home' )
    ->where( 'post_id', '=', get_option( 'page_on_front' ) )
    ->add_fields( array(
      Field::make( 'text', 'a_text_field' ),
    ));
}