I was interested in Dr. Seong-Hun Kim's Technique Clinic, "Prevention of Gagging with a Modified Krol's Method" (JCO, October 1999), in which the patient is asked to lift their leg during an impression.
Like Dr. Krol, I learned to take impressions with the patient lying down or semi-supine in a dental chair. I did this for 30 years, until one day I discovered that it was far easier if the patient sat upright with the neck vertical, the head horizontal, and leaning forward over the nearest sink. Running water in the sink greatly relaxes the patient and enables us to rinse the patient's mouth out before and after the impression. Asking the patient to squeeze their nostrils with their left hand forces them to open their mouth and breathe through the mouth as the impression is taken. This reverses the gagging reflex. With the sink, it doesn't matter if the patient does gag.
I now take all my impressions with the patient in front of the sink, and find the impression technique is easier and the patient is more relaxed and less panicked, especially when the upper impression is taken. The reason is obvious: in the supine position, gravity drags the alginate down the throat. In the upright position, with the neck vertical and the head horizontal, the alginate falls onto the floor of the mouth instead.