Use this PowerShell script to create a bootable USB flash drive from an ISO file. Modify line 3 to point to your ISO file. I did not write this PowerShell script. I found this PowerShell script at https://p0w3rsh3ll.wordpress.com/2016/10/30/how-to-create-uefi-bootable-usb-media-to-install-windows-server-2016. 

Wait until The operation completed successfully is displayed before removing the USB flash drive from the PC.

# minimum size of USB stick 5.29GB

# Set here the path of your ISO file
$iso = 'C:\Users\john.doe\Downloads\en_windows_server_2016_x64_dvd_9327751.iso'

# Clean ! will clear any plugged-in USB stick!!
Get-Disk | Where BusType -eq 'USB' | 
Clear-Disk -RemoveData -Confirm:$true -PassThru

# Convert GPT
if ((Get-Disk | Where BusType -eq 'USB').PartitionStyle -eq 'RAW') {
    Get-Disk | Where BusType -eq 'USB' | 
    Initialize-Disk -PartitionStyle GPT
} else {
    Get-Disk | Where BusType -eq 'USB' | 
    Set-Disk -PartitionStyle GPT
}

# Create partition primary and format to FAT32
$volume = Get-Disk | Where BusType -eq 'USB' | 
New-Partition -UseMaximumSize -AssignDriveLetter | 
Format-Volume -FileSystem FAT32

if (Test-Path -Path "$($volume.DriveLetter):\") {

    # Mount iso
    $miso = Mount-DiskImage -ImagePath $iso -StorageType ISO -PassThru

    # Driver letter
    $dl = ($miso | Get-Volume).DriveLetter
}

if (Test-Path -Path "$($dl):\sources\install.wim") {

    # Copy ISO content to USB except install.wim
    & (Get-Command "$($env:systemroot)\system32\robocopy.exe") @(
        "$($dl):\",
        "$($volume.DriveLetter):\"
        ,'/S','/R:0','/Z','/XF','install.wim','/NP'
    )

    # Split install.wim
    & (Get-Command "$($env:systemroot)\system32\dism.exe") @(
        '/split-image',
        "/imagefile:$($dl):\sources\install.wim",
        "/SWMFile:$($volume.DriveLetter):\sources\install.swm",
        '/FileSize:4096'
    )
}

# Eject USB
(New-Object -comObject Shell.Application).NameSpace(17).
ParseName("$($volume.DriveLetter):").InvokeVerb('Eject')

# Dismount ISO
Dismount-DiskImage -ImagePath $iso