Tested with Windows Server 2016.

This lists the quick steps to create a bootable Windows installer on USB disk without using extra tools.

Follow Thomas Maurer - Create a USB Stick for Windows Server 2016 Installation.

In short:

1. Start an elevated command prompt:
2. Start diskpart and use it to:
   1. List the disks.
   2. Select the USB disk.
      1. In this example the USB disk is on disk 1, please check your output of list disk to determine which number the USB disk is on before proceding with select disk.
   3. Clean the USB disk.
   4. Create one primary partition.
   5. Format that partition with FAT32.
   6. Mark the partition active (bootable).
   7. Assign the USB disk a drive letter (K: in this example).
   8. The below commands assume the USB disk is disk 1, with the only other disk being 0 the OS disk.

      diskpart
      list disk
      select disk 1
      clean
      create partition primary
      format fs=FAT32 quick
      active
      assign letter=k
      exit

3. Mount the Windows server 2016 DVD (i.e. double-click the ISO in explorer to have it mounted on for example D:\ as in this example).
4. Copy the contents of the ISO to the USB disk.
   1. Skip install.wim as we need to split it to overcome the FAT32 max 4 GB per file limit.
   2. Skip autorun.inf to prevent an on-access anti-virus scanner from interfering.

      robocopy d:\ k:\ /E /XF install.wim /XF autorun.inf

   3. Split the install.wim in max 4 GB pieces and write those pieces to the USB disk:

      dism /Split-Image /ImageFile:D:\sources\install.wim /SWMFile:k:\sources\install.swm /FileSize:4096