@slick: if I understand it correctly, you want to use the controller in AP mode (without another router). This is possible. You have to either use the OpenSprinkler mobile app, or as KSprinkler75 said, download the OpenSprinkler app from github, and run its index.html. This is NOT the same as typing 192.168.4.1/index.html — the correct approach is to open the index.html in OpenSprinkler app folder.
You can of course also write your own front end interface, using the OpenSprinkler HTTP API. In fact, as I explained in this post:
https://opensprinkler.com/forums/topic/useful-script-for-testing-opensprinkler-api/
the testing script is a simple front end (not much features other than just testing a subset of the HTTP API) and you can obviously improve it significantly to make it more usable.