Speaking of clay...I've had students build a cross-section model of the earth's inner layers in conjuction with the story: How To Dig A Hole To The Other Side Of The World, by Faith McNulty.
As you read this story to your students (assign students into teams of two) each team will model the different layers of the earth using clay as described in the story: core (small marble- sized ball) in a red clay, inner/outer mantle (surround the core with a different-colored layer of clay about 2" or more thick), and the crust (thin layer of blue-colored clay about 1/4" thick covering all of the mantle layer). When the story/models are completed, students (with a piece of string or a plastic knife) then cut the earth model in half. Each person then gets a "hemisphere" ....and students make little labels for each of the earth's layers (attach label to a toothpick or straight pin) and insert into the clay to identify the earth's inner layers. Great 3-dimensional geography/art projects for displays and take home.
I found a few more lesson plans (with lots of extensions) that relate to teaching about the inner layers of the earth. These lessons also use: "How To Dig a Hole to the Other Side of the World."
Realistically, we could not dig to the other side of the earth....but if we could? The following fun websites below will show you where you would exit (antipode locations) ...if you could dig to the other side of the world!!!!!