My wife baked two 9"x13" cakes. I used one for the base. The second one was used for the hillside. I cut the second one in 1/2 diagonally and then cut...
For my daughter's 5th birthday she wanted a cake inspired by the movie "Brave". She didn't have any specific design or plan in mind so I just winged it.
Step 1: Come up with a design
I like making sketches for almost anything I make/build before I build it. It keeps me focused on how I want the end result to look. It doesn't always come out exactly the same, but the basics are there.