Did you notice the mudra of the bin in the kitchen corner, the mudra of trees and flowers, the mudra of a car passing by? And what is your original mudra? Do Buddha sit in a beautiful Japanese garden or appears and vanishes every moment in everything and everybody you meet? Do we have to copy the posture or outside form of statues or teachers or rather let the real thing manifests itself through our clumsy lives? Our Soto form is very simple, yes, as Jundo puts it we do something with our hands but not flourishy, over complicated, it is almost a circle and it embraces all things. Out of this the ten thousands hands of Kannon with raise through the day, Kannon washing the dishes, cleaning her b.., giving or taking...to this the ten thousands mudras of Kannon-you-me-everybody will return. Our way is to practice putting our hands like that and do this until we die and beyond, which is every now. Even the ton of literature on the subject won't help you to understand. even the pages I could write on this would be useless. Because you are invited as Keizan says in Zazen Yojinki:
When the mind scatters into distraction, place attention at the tip of the nose or at the tanden. After this rest attention in the left palm. Sit for a long time and do not struggle to calm the mind and it will naturally be free of distraction.
To rest your mind in the mudra means to let the mudra doing you, forming you, forgetting you. Some folks think it means that we put the attention there during sitting, yes and no, it means much more than that. Just go there by yourself, and forget yourself in there. The Dai Butsu of Kamakura you like so much is just a blossom coming out of your very eyes.