This is what I did,
1. Tools->new config
2. Open a terminal as root. Where sd? is the actual drive device name, for each drive perform, # dd if=/dev/zero of =/dev/sd? count=640k
Note: This will erase the drive configuration and partition tables. To completely wipe all data on a hard drive, omit the count option. Depending on the drive, it could take several hours. SSDs may have a different drive prefix and need a special wipe utility for a secure erase.
3. Flash the USB stick with the latest Unraid USB Flash Creator.