This is an adorable cake she has chosen. No offense to Valley Cool Cakes, but that procedure will not give you the look of the cake in the pic. The cake in the pic has more of a 3d look.
I think your fondant will look more like on the cake in the pic if you roll long ‘logs’ of each color. Since you are new to this, it may help you cover the cake with fondant first and then use gumpaste glue to attach each log diagonally as in the pic. This way your icing won’t pull away with the weight of the logs. Slightly flatten each log so it won’t be so rounded.
It should be interesting to cut with all that fondant, so don’t make the logs too thick. Post a pic when you’re done. Good luck.