There are tons and tons of sewing machine cakes on the Internet, but not many of them show you how to create the insides of the cakes. Most of them use Rice Krispies to make the structure but this one shows you how to make the structure using styrofoam to make it a little bit sturdier.
If you instead want to learn how to make a sewing machine cake from scratch, you can read it here.
If you want to know more about the structure of the cake, learn it here.