ftp://ftp.slax.org/SLAX-6.x/rc3/README.usb-iso
If you need both TAR version (for your USB drive) and ISO version (for CD), you don't have to download both.
Here is how to convert it from one to another:
If you downloaded ISO file and you wish to convert it to TAR version
mount the ISO somewhere
eg. mount -o loop slax.iso /mnt/tmp
make the TAR easily (or copy the content directly to USB)
eg. cd /mnt/tmp; tar -c boot slax >slax.tar
If you downloaded TAR file and you'd like to generate ISO
unpack the TAR archive
eg. tar -xf slax.tar; rm slax.tar
run make_iso.sh to generate the ISO file
eg. cd ./slax/ ; make_iso.sh /mnt/sda1_disk/slax.iso