Clay can be found in our soil, but it is also inexpensive to purchase, especially self-drying children's clay. I think I would use papier-mรขchรฉ for this (you can soak pieces of toilet paper rolls or other cardboard in water, mould them, and glue them on).
I would love to see what you used and the proportions.
I am curious to see what you will do with the end result. Is there an endresult since I only see flowers painted on your hand.