Howdy Your Magesty
Slackware, too, has
live iso images that can be burned to dvd or usb thumbdrives to test drive slackware on your hardware.
To boot from such a device, sometimes the boot order configuration needs to be edited in your hardware's system bios, to make sure that it boots from usb over internal, should both be present. Also, there is usually a key that, if pressed down while powering on, will bring up a menu of available boot devices; but this key varies from device to device, however it often is f2, f10, or esc.
Are you wanting to dual boot with Windows 10?
I use fdisk, gdisk, or parted to examine and edit partition tables of disk drives--windows probably has a partition editing tool too, but I don't care about windows, so have no idea what it is.
But to use EFI successfully, there must be a partition with type EFI System. This partition gets mounted to /boot/efi and contains a directory called EFI, which contains subdirectories for the different operating systems you wish to boot. Slackware installer creates /boot/efi/EFI/SLACKWARE, and populates it with efi firmware, elilo.conf, initial ram disk, and the kernel. You can also put what I just listed into /boot/efi/EFI/BOOT, though renaming the firmware BOOTX64.efi (that is assuming you have a 64 bit cpu), as a backup, because all the efi boards are supposed to check there.
You could boot from the live slack iso, and then use one of the above mentioned tools to print your partition table and verify that there is an EFI System partition. Create one if it doesn't exist. Format it with FAT32.
However, usually the Slackware installer takes care of all that for you. But if you want to check up on it, you can do so manually by the methods mentioned above.
Cheers, and welcome to Slackware.