The major document I read was wfastcgi on pypi: https://pypi.python.org/pypi/wfastcgi
I also googled with these key words "python flask iis"
http://netdot.co/2015/03/09/flask-on-iis/
https://heejune.me/2015/04/22/running-python-flask-on-a-local-iis-not-azure-with-wfastcgi-py/
Most of the examples I have gone through were with blankets in WSGI_HANDLER value. We followed that and failed.