No.
I routinely make a partition (and maybe format it) before installing
Slackware. It notices that there are some existing partitions, asked if
I want to use them.
The installer can't move forward until you specify a partition to install
to, so it can't be that you clicked something too fast.
Likewise, plenty of times, I've deal with lilo later. (And definitely
lilo would have nothing to do with fstab).
I cna't see how you got an install without udev or fstab.
Michael