it's actually easier: first you connect it by usb, then depending on the phone setup (android version and user preferences) it will ask on connection if you want to activate "usb tethering" (you want this).
if it won't ask it, go in the settings -> wireless connection menu and you should find the usb tethering option: if it's not activated, activate it from here.
then you should have a new unconfigured network interface usb0 in your slackware, you can check it by "ifconfig -a".
fire up the dhcp client for it
and this will do.
I'm posting this using my phone this way
(I'm on holiday)