What a way to receive oral; the receiver being subtly restrained makes it all the more exciting! Instructions for how to arrange yourself are the same as Suplex - His.
Make sure that the couch height isn't too high, and have positional aids or pillows on hand to make it more comfortable for the person lying on the ground. In addition, have the receiver evenly distribute their weight to their neck and shoulders. The receiver can grasp the others ankles for leverage or simply lay their arms down at their side, palms flat, allowing them to lift their hips to meet the mouth more readily.