Those people tend to be impatient to gain speech, steamed up with their determination as they practice, and would not listen to a theoretical guidance.
Instructors would teach them at a voice training class to put a pressure on a part a little lower than the curve under the chin and the throat so that the voice will be gained quickly. This explanation is easily understood by the trainees. I myself have the experience of successfully instructed trainees by this explanation.
It is very important to tell beginners not to leak the air through the opening in the neck in utterance, however, it is also natural that they do not understand it. It is another difficulty to explain how to prevent the air from leaking through the opening.
