Place first layer of cake on cake tray. Spread a layer of icing on the top.
Place second layer of cake on a separate plate or tray. Using an upside-down martini glass (or small bowl) cut out a circle of cake from the centre. Eat the centre of the cake, for quality control purposes. (Yum!)
Place second layer of cake on top of the first layer. Ice the top of the second layer of cake (i.e. the ring of cake that is all that is left of the second layer).
Fill the centre of the second cake layer with candies. Pack them in firmly. You want there to be lots of candy to spill out when you remove the first slice of cake.
Place the third layer of cake on top of the second layer.
Ice the top of the cake. Thinly ice the sides of the cake, using an offset spatula (or the edge of a very straight knife, or just a ruler) to scrape off the excess. To get the look of a naked cake, you want to be able to see the layers of the cake.
Using a pinch of sprinkles at a time, throw sprinkles at the bottom edge of the cake (I usually do this over a sink, while firmly holding the iced cake on a slight slant to give the best access. Note that the cake has to be pretty chilled to be able to do this without the layers slipping off. Another reason why chilling the cake layers helps keep the cake together!)
Using the silver dragees, make a question mark on top of the cake.
Using the leftover sprinkles, sprinkle them over the top of the cake.
Chill the cake thoroughly before serving. Then, cut a slice, plate it, and listen to the cheers of the onlookers as they find out the sex of the new baby! (You'll also hear appreciates mmm's as they eat that delicious buttercream-covered cake!)