I've made a few diaper cakes in the past, so I stuck with my tried and true method. Roll tiny diapers (either size nb or one) and hold the roll with small piece of scotch tape. I always build the bottom base around a pack of wipes, because what new parent doesn't wish they had more wipes?
I usually aim to have the bottom base consist of 20-30 diapers on the outside ring, and build the next two tiers smaller than the previous. Fasten each diaper tier with a tie (either yarn or string- anything will do because it will be covered up) Don't worry about the tiers being perfect, you will fix that later.
After you've built the actual cake, the fun part begins- decorating! I wanted something simple, clean, and modern. I also wanted a cake that would work for a boy or girl, since the couple is having boy/girl twins. I chose to wrap the cake in yarn with a variety of teal colors. When you start wrapping your cake, tie the yarn to your existing tie that is holding all the diapers in a circle. Like so:
|The finished first tier|
I used two colors on the second and third tiers to give the cake an almost ombre affect:
|The finished second tier|
Simply place one tier on top of the other to create your cake. I don't do anything to fasten the tiers together and they seem to stay put fairly well.