I installed kernel-huge-smp (no need for initrd)
This is where you went wrong.
You will need an initrd that contains the mdadm and lvm binaries because your root partition is on that LVM (which is in turn built on RAID).
There are two good README's in the Slackware tree's root directory:
If you have not read those yet, I suggest that you do so now.
If you want to have a script that runs a check of your system, download mkinitrd_command_generator.sh
and get it into your installer environment in some way (floppy, USB stick, or after enabling the network use wget).
What you need to do is boot from the Slackware CD, wait until you reach the command prompt, and do not start 'setup'.
Instead, configure your RAID and LVM again so that the partitions become available, then mount all of those partitions at /mnt , and if you have that mkinitrd_command_generator.sh script copy it into /mnt/root/.
mount -o bind /proc /mnt/proc
mount -o bind /sys /mnt/sys
In the chroot you can generate a new initrd.gz, then run lilo, reboot and hope for the best.
The mkinitrd_command_generator.sh script can help in determining the correct "mkinitrd" command... try running
in that chroot environment and examine the output.