So the installer that ships with slax doesnt actually work (Atleast not on virtualbox) to install it to a Virtual box hdd I had to take a few steps which took a bit of tinkering to get just right to allow the slax hdd install.
First you want to find the virtual hard disk in slax: fdisk -l should give something like /dev/sda
Next is to create a partition table and the partions: best look this up using gparted or fdisk (both on slax)
after that mount it, i always create a dummy folder in /mnt/ called my_drive or similar: mkdir /mnt/my_drive && mount /dev/sda /mnt/my_drive
Do a recursive copy or using the GUI drag the /slax folder from the ISO or cddrive: cp -r /mnt/live/memory/data/slax /mnt/my_drive/
Now at this point I had to move the all the files to a folder called slax EXCEPT the /boot folder mkdir /mnt/my_drive/slax && mv *.sb /mnt/my_drive/slax/
Your Hard disk drive should look something like this:
Then you go into your boot folder and alter the syslinux.cfg:
Mine ended up get changed to this,
APPEND root=/dev/sda initrd=/boot/initrfs.img load_raddisk=1 prompt_ramdisk=0 rw printk.time=0 slax.flags=xmode,perch
after that its a matter of running that broken bootinst.sh to run the syslinux bootloader installer. cd /mnt/my_drive/boot && ./bootinst.sh
Reboot the VM and it should boot from the harddrive.