For a more detailed story on how they ran their manufacturing, regarding armored vehicles in particular, there is a fascinating story about The Workshop

The facility would perform a wide variety of overhauls and upgrades on nearly all types of armoured fighting vehicles in use with the Islamic State, ranging everything from installing multi-spectral camouflage on tanks to the up-armouring of AFVs and even constructing modular turrets for installation on four-wheel drive vehicles such as the Toyota Land Cruiser.

http://spioenkop.blogspot.se/2017/08/armour-in-islamic-state...

That blog has several really interesting articles about DIY armour and fighting vehicles.