Because Apple intentionally closed the jailbreak holes in 9.3.6 (released long after 9.3.5), finding an method is extremely difficult.
There is no untethered jailbreak for iOS 9.3.6, and there likely never will be. ios 9.3 6 jailbreak untethered
: Alternative semi-untethered tools for 32-bit devices. Installation Overview Because Apple intentionally closed the jailbreak holes in 9