3.
Insert a skewer into the dummy. Take it out and insert it in a couple of times to widen the hole slightly. That way you will be able to easily take the topper out of the dummy later.
For the purpose of the tutorial I used a shallow dummy, but I suggest using a deeper dummy and leaving the skewer longer (insert it all the way down), so that you can trim it to the depth of the cake later. That way the topper won't lean to the sides once attached to the cake (heavy head).