Handprint Mold Tray

Recently had a baby so for mothers day I wanted to gift my mother and now first time grandma a clay imprint of her sons hand print with her grandsons print in the palm. The store kits were good for an infant but not an adult so I bought a brick of clay and made my own. My biggest concern was that it wouldn't fall out overtime so I added the holes which serve 2 purposes, allow air to escape and then when you press into it on a hard surface they are chamfered which creates a hold of the clay to the tray. The cross section of these however aren't huge and I was struggling how to mount this so then I decided I would also add some cone shape pieces to the inside that will be inside the clay which should never release. Within theses I also added m4 thread inserts so it could be hung inside a shadow box or I could whip up some legs and bolt them on that way.