Although i think its not "best practice", it is possible:
#create the USB Installer
-Download the OS X High Sierra installer via the App Store, it will be installed into the /Applications directory
-If it opens automatically, close it
-Insert a USB stick (8GB+)
-Run the following command where MyVolume is the name of the USB volume:
sudo /Applications/Install macOS High Sierra.app/Contents/Resources/createinstallmedia --volume /Volumes/MyVolume
# boot the USB installer
-Boot the computer holding the Option key
-Select the USB installer as the startup disk
-Open Utilities > Disk Utility and make sure that the internal SSD/HDD is properly formatted (e.g. in HFS+ or APFS), named (Macintosh HD) and erased
-Close the Disk Utility and
-Open Utilities > Terminal and type the following:
"/Volumes/Image Volume/Install macOS High Sierra.app/Contents/Resources/startosinstall" --volume “/Volumes/Macintosh HD” --converttoapfs NO --agreetolicense
-By use of that command the machine will restart and install macOS High Sierra without APFS conversion. (for APFS conversion you can simply use "--converttoapfs YES" or don't use that command
This method was tested on 10.13.5 and 10.13.6.
