There are two things you can do to make your recommendation letters hollow, nothing, vacuous. First, let it be too general. Let it look like someone writing about you seeing from a mile distance. No specific details about you, your past, your achievements. Let it say you have the potential, but not say why. Let it say you have amazing work ethic, and stop with that with no clear example to support it. The second is let the recommendation letters leave out the weaknesses in you completely. Let it be only about the perfection in you. Let it not strike a balance between the strength you have and the weaknesses that you are vulnerable to, as do normal mortals have. If you recommendation letters has these two in them, you are sure to have done to make them just an empty paper and not an advocacy document. If you really want your recommendation to be believed, let it be specific, let it contextualize the claims it makes, let it be more human, covering your dominating strengths while not ignoring the weakness. What is great about weaknesses is that it makes us more human, and our narrative more credible.