I have been closing the right eye, listening only with left ear, trying to imagine the words right to left, while watching Nat sing, studying the left side of his face, and trying to mouth the words with the left tongue. The back of the left tongue feels on the cusp of joining the party. I think it is where the styloglossus attaches to the tongue and for many sounds I imagine it has to relax and lengthen to sound left (right). I don't feel there is a good differentiation between my jaw and tongue on the left rear side at present.
Doing the above creates a tension on both side of the lower jaw. It is like I am fighting an existing tension to allow for a different use of tongue and jaw musculature. Almost like I go through life with the left tongue tied behind my back.