Image orientation in vtk-dicom is briefly described here. This link is focused on the “reader” and doesn’t talk much about the “viewer”.
In general, you are correct that getting the correct image orientation in the viewer is a matter of properly positioning and orienting the camera for each view. But I haven’t ever really looked at the Qt FourPaneViewer example so I can’t say how it would have to be modified to provide the views that you require.