I to am a linux newb, but I think that I can help. Boot from your slack CD and you will be presented with bash( or something that looks like it)
1) type: fdisk /dev/hda (or whatever you are using as the harddrive) You can find out the name of your disk by typing 'fdisk -l'
2) then use the 'd' command and delete all the partitions on your harddrive.
3) Next use the 'n' command and add to add the two partitions.
4) Then you will need to change the id of one of the partitions to swap( I forget the command for this )
5) then type p and make sure that both partitions exist, they are the sizes you want, and one is of type swat and the other linux.
6) Then type 'w' to save and exit
7) You will be returned to bash, then just type 'setup' and use slack to format both of the partitions.
I hope this helps and good luck