I'm writing this here because I keep forgeting how to do it and there are several articles out there that are either outdated or slightly wrong.
There is a solution using unetbootin , one with bootcamp assistant and one using mounting and manually copying files but none of them worked for me.
This solution worked for me in macOS High Sierra and Mojave and it will probably work on other versions.
First you have to convert the windows iso file to an img:
hdiutil convert -format UDRW -o windows.img windows.iso
The result of this would most likely be a file named widows.img.dmg. The next step is to unmount the usb disk ( diskutil list to see which one it is , in my case this was /dev/disk2 )
sudo diskutil unmountDisk /dev/disk2
Now just use dd to copy the image to the usb device:
sudo dd if=windows10.img.dmg of=/dev/disk2 bs=1m