the below is an excerpt from here
http://slackware.uk/slackware/slackw...EADME_UEFI.TXT which is part of slackware documentation
If the menu entry doesn't work on your system, you can still force your
machine to boot ELILO automatically by copying the files in /EFI/Slackware on
your EFI System Partition to /EFI/BOOT on your EFI System Partition, and
renaming /EFI/BOOT/elilo.efi to /EFI/BOOT/BOOTX86.EFI. Before doing this,
you might want to back up any existing files in /EFI/BOOT.
The above might be the solution for you issue , it also works for grub. But with the .efi file from grub.