Please tell us what Slackware version you want to install: Slackware 14.1 (32 bit) or Slackware64-14.1?
Anyhow you need to have a partition formatted to ef00 *only* if you have an EFI firmware, else you don't need than, even with a GPT instead of a MBR.
Also, it would be better to ask your question about your two hard disks in the same thread and in any case please tell us what you want to use the 2TB HDD for (assuming that you want to use
the 500GB HDD for / (root) at least.