How to make a bootable dvd of High Sierra
(note it only boots as hfs+, not apfs):
Make the bootable iso with the following commands:
hdiutil create -o /tmp/HighSierra.cdr -size 5130m -layout SPUD -fs HFS+J
hdiutil attach /tmp/HighSierra.cdr.dmg -noverify -mountpoint /Volumes/install_build...