3Ware cards do not always make it easy to export drives as JBOD, or for single drives. To get this working it needs to be done through the 3Ware CLI (tw_cli on Linux):

tw_cli maint createunit c0 rsingle p0

Where c0 is the first RAID card in the server, and p0 is the first drive on the controller. You need to run this command for each drive you wish to set to JBOD.