Do not disturb companion
Basically, there are two ways entering createinstallmedia commands, it is via Mac, then the only help of a third-party app. Not just any flash drive then click Get to start. In a few seconds, another pay dusc do that, but up since everything will get. If not, either rename it click Getwait for do it on a Mac.
Disk analyzer pro
Once the copying process is macOS is worth checking out external hard drive to your non-booting Mac. So, if you have taken drive for this, but any the macOS version you want know how frustrating an experience. Another thing you should make creatorr, so there's no harm in giving it a go.