To boot a VirtualBox virtual machine from a USB device, we must first create a disk that maps to the USB drive with the command below
VBoxManage.exe internalcommands createrawvmdk -filename C:\path\to\your\HardDisks\USB.vmdk -rawdisk \\.\PhysicalDrive1 -register
Note: Use Disk Management or Diskpart to determind the number to follow “PhysicalDrive”
Now we can simply make this drive the “IDE Primary Master” under storage, and boot from the USB Device.
Thanks goes out to this blog post for providing the solution!