Building a tiered cake requires more than simply stacking layers of cake on top of one another. Cake is heavier than it appears and stacking cake without proper supports will cause any cake to buckle down on itself. If the cake buckles, you will be left with a crumbled pile rather than an elegant tiered cake that stands tall at any event. Cakes with more than three tiers need a single support that runs the entire height of the cake to reduce tilting. For a three-tiered cake, you will need to add supports to the bottom and middle tiers.
Place the bottom tier of the frosted cake onto the cake board. Be sure to centre the cake in the middle of the cake board; if you position the cake off-centre, it will be difficult to balance the cake when you move it from the assembly location to the event site.
Measure the height of the bottom tier and cut four dowels to the height of the tier. If you're cutting wooden dowels with a hand saw, use a small table vice to hold the dowel tightly while you cut. If the dowel is not held firmly enough, it may splinter, creating an end that is not level. Cut plastic dowels with a sharp utility knife or a serrated knife. If using a utility knife, set the dowel on a flat cut-resistant surface and cut through the dowel for a clean cut.
Mark where the second tier will sit on the bottom cake tier, using a toothpick; make slight impressions into the frosting where the tier will sit. You do not want the marks to be visible once the second tier is in place, so limit the number of marks you make.
Press the dowels firmly into the bottom tier of the cake. Arrange the dowels in a square shape for optimal support. Ensure that you position each dowel within the area you marked for the second tier. If the dowels are not inserted where the second tier will sit, they will not support the weight of the cake. The top of the dowels should sit flush with the top of the cake so they will not be visible once the second tier is set on top.
Repeat steps 2 through 4 for the second tier. Once you have inserted the dowels into the second tier, position it on the bottom tier so it is sitting above the supports. For a three-tiered cake, do not insert supports into the top tier. Stack the final tier on top of the second tier, making sure to set it on the supports you inserted in the middle tier.
You can also use hollow plastic straws to support tiered cakes. Cut the straws to size with scissors; choose strong straws without accordion bends. Larger cakes may need more than four support dowels; insert a fifth dowel in the centre of the cake if needed. Smaller cakes may need only three support dowels; arrange the dowels in a triangle shape if you choose to use only three.
Make sure the dowels are made from food-grade or food-safe materials so you do not contaminate the cake.