Installing Arch directly from Slackware
 

Hey,

I want to install Arch to my empty partition.
But I don't have empty flash drives nor I own any CD's/DVD's nor I have capability to read/write to 'em.

So installers are basically unpacking stuff so why one can not install directly from CLI?

You can mount your empty partition and install ArchLinux using 'pacstrap' as described on their wiki.

Please note that this method includes installing 'pacman' and some other necessary stuff on your system so you can set-up Arch from within your Slackware.