Clay is the material that takes any shape, so dream books read it as potential and as a self still being formed. Working it with your hands points to shaping your own circumstances.
Where in your waking life have you met something like this lately?
My Cosmic Code has a private dream journal. Write a dream down and the app picks out the symbols in it, shows what dream books say about them and, over time, which words recur across your entries. The journal is stored on your device only.