How to get spotify native on slackware.
Navigate to http://repository.spotify.com/pool/non-free/s/spotify/ and download the approriate .deb file for your architecture.
spotify-client-qt_0.6.6.10.gbd39032.58-1_<ARCH>.deb at the time of the writing.
Extract the .deb files using the ar command
ar vx spotify-client-qt_0.6.6.10.gbd39032.58-1_<ARCH>.deb
Now you should have a file called data.tar.gz that contains the files that you need. Extract that
tar zxvf data.tar.gz
Now you should have a folder called usr. cd into that folder and as root, copy the binary and theme files into the approriate places.
cp bin/spotify /usr/bin/ cp -R share/spotify /usr/share
Now you can execute spotify and voilà. It should start