First, I used two 9" layers and two 10" layers, and they were stacked and dowelled like a regular two-tiered cake. There was a 7" board and dowels supporting the two top layers. The board was 7" so that I could carve down the sides of the cake without worrying about hitting the board.
Next, I carved the general shape of the pumpkin.
While the orange dried a little, I painted in the facial features.
After that I brushed some darker oranges and browns onto the grooves to give it more depth of color.
Then I added the baby wearing a witch's hat. You can substitute a stem here, or if you want to stay with the Halloween theme, a little ghost or a regular (non-baby) witch.