Use fdisk or equivalent to prepare the USB disk (at least 7G).

Remove any existing partition (d), create a GPT table (g).

Add a UEFI partition 1G sized, and 6G++ one of type 11 (Microsoft basic data).

Save the partitio table (w).

Format the UEFi partition and the NTFS one :

mkfs -t vfat /dev/sdZ1
mkfs -t ntfs /dev/sdZ2

Download a Win10 CD from Microsoft and mount it with :

sudo mount -o loop -t iso9660 /chemin/vers/image.iso /mnt

Then :

• copy /mnt/sources on /dev/sdZ2
• copy all other files and directories on /dev/sdZ1
• finish by creating sources directory in /dev/sdZ1 and copying sources/boot.wim in it

(WARNIN : not tested!)

(source from https://techbit.ca/2019/02/creating-a-bootable-windows-10-uefi-usb-drive-using-linux/ where can be found less arid instructions…)