Rev. Taigu offers a few more perspectives on the “sitting” of “just sitting.” He says:
Sitting on a cushion is what we normally do. The actual flexibility of this cushion called a zafu makes it possible to position it at an angle which makes sitting much more comfortable. A zafu is a very personal item and one should search around to find the right thickness for the cushion. When putting hands together to form the zazen mudra, we usually put the left hand on top of the right, palms up and thumbs very lightly touching. If you are not using a koromo, which is a black robe with huge sleeves, then you may use a towel and put it on your lap to support the mudra.