If I'm making a cake with only 2 tiers, do I need to use dowels/a cake board on the top level or can the bottom tier (probably 3 levels of cake) support a top tier (another 3 levels)? Thanks for your answer.
Yes, its very important NOT to skip those steps....it will prevent a disaster.
dowel and cake board! the top cake will sink into the bottom cake.
Make sure you use enough dowels. My first fondant cake was exactly what you described, 2 tiers and 3 layers of cake in each. I only used 3 dowels, basically in the shape of a triangle because the top tier was small (6 inches). During the 15 minute transport, it shifted, causing it to lean to the right and wrinkling the fondant.
It was for family, and they thought it was cool because they're not used to tiered cakes, unless it's for a wedding, but I was heartbroken.
I tried 3 times to attach a photo...very frustrating.
Yes, you must support the upper tier. SPS is the best choice, but if you can't get that, the the W Hidden Pillars will do, or dowels as a last resort. But yes, you must support the upper tier.
You definitely need to use a cake board and support of some sort. If you dowel, I use the rule of one dowel per "inch" of cake. For example if I am supporting an 8in. cake I would use 8 dowels to hold it up.
I use 4 dowels only, no matter what size the cake is. It's worked fine for 30 years. Too many dowels will turn the cake into swiss cheese, damaging the structural integrity of the cake, causing a crumbly mess when you "try" to cut it. Trust me .... been there .... saw that .... cussed the entire time I was cutting this other person's cake who used too many dowels.
I would definitely use dowels.
I use the straw method and the dowels through the middle.
For an 8in tier I would use 4 straws in the bottom layer and dowel through the middle. I have yet to have any of my cakes fall, split, wrinkle, etc.