SlackBuildsOrg/system/efi-sync

efi-sync is a program which will update your efi when your kernel or its
related files are updated.

To have efi-sync to start and stop with your host, add to the beginning of
/etc/rc.d/rc.local:

  if [ -x /etc/rc.d/rc.efi-sync ]; then
    /etc/rc.d/rc.efi-sync start
  fi

and to /etc/rc.d/rc.local_shutdown (creating it if needed):

  if [ -x /etc/rc.d/rc.efi-sync ]; then
    /etc/rc.d/rc.efi-sync stop
  fi

Also ensure your EFI is mounted on boot by having its entry configured in
/etc/fstab. For more instructions, refer to the project's README in this
packages documentation under /usr/doc.