This challange is not about to model what do you see, but to NOT model what do you NOT see.

This time, dimensions are irrelevant. I will add them, should you prefer to follow specific.

Create a cake bed (100x100)
Add u-shaped frosting (10x10x10) four times and space frostings equally.
Add the same frosting pattern to the perpendicular axis.
During this whole process focus on the outside of the frosting layer should be smooth - nothing, that shouldn't is sticking out.

If you want to challenge yourself a little, try to do this in as little timeline steps as possible. I did it in 14 and it could be done in less.