Creating a new map layer is just as easy as it is to create a normal StatelessWidget or StatefulWidget.
Only one method call is needed to 'connect' the widget to the map state: FlutterMapState.maybeOf(). This call does two important things:
Cause the widget/layer to rebuild automatically when required (if in the build method)
Expose the map's internal state, meaning that it's information (such as zoom) can be accessed
You can see an example of how this is done below:
Attempting to use the widget above outside of a FlutterMap widget will result in an error.
The FlutterMapState.maybeOf method will return null, because it cannot locate a parent/inherited state, and therefore cause a null exception.