I have two or three that I use.
The first involves the wedge christie. It's the way I teach L2 candidates how to make a proper wedge christie without pushing a stem up the hill. You (the instructor) make a diagonal traverse and draw a nice deep gouge in the snow ith your pole. Then have your student ski immediately below that line (maybe 3"-6" from the line). They should be in an appropriately wide stance for a wedge christie. They then need to make a wedge christie without letting the tail of the uphill ski touch that line. The only way to get that inside ski to flatten gradually (as opposed to trying to make a paralle turn with a forceful tipping of the inside ski), is to move the CM in that direction.
Another method starts as a static exercise, and can be done with anyone from a wedge turner to a dynamic parallel turner. Have the student stand still on the slope. You stand in front and below the student facing them. Take the palm of your hand or the soft end of your pole, and hold it about 2"-3" in front and slightly below the student's downhill hip bone. Ask them to try to touch your hand or pole with their hip. As they move their hip toward your hand, keep moving your hand away, so that it remains about 2" in front of their hip. This causes them to lead into the turn with their CM/hip, as opposed to their skis. If you do this on gentle terrain, using your pole grip instead of your hand, you can make turns going backwards in front of them as they keep chasing your pole with their hip.
I've also had some success with some students by having them ski about 5 feet behind me (almost tip to tail), and telling them to just try to move their hips/pelvis directly at me, but make sure their skis stay in my tracks. Since I am just ahead of them in the turn, they move their body in the right direction. The biggest problem I have with this, is that you need to have people who are willing and able to ski immediately behind you. A lot of students wait for you to ski away, then wait a few seconds before they start moving. This will put them too far behind you.