Hello! 

So I've never shaped this type and I;m getting nervous to do this because I don't have time to screw it up!

It's for my cousins friend and she's so exited about this cake so I don't want to let her down. 

She needs it to serve about 20-25.  So I planned on making  3 layers of 10" round for the bottom and 3 layers of 8" round for the top.  

Just don't know which way or technique is best to do the road part. 

Should I bake the top and bottom as 6" and 8" and back maybe like a 10" just for the ramps and attach them with buttercream? 

or go with my original idea to bake bigger and cut the cake?

Thanks!!

Well, if you bake the bigger cakes you gonna end up with a lot of left overs. Obviously you would need to charge for them...if you charge at all. It will definitely look more natural as it would still look like 2 rounds (looking down on the cake). You should get enough servings with a 6" and 9".

Otherwise you could make a 10" and a 6", attach a single layer 8" (cut into thirds and on top of each other, then cut to fit)  which would make the cake at least 8" or 9"  wide on one side, depending how wide you want the ramp to be. That's why you need at least a 10" cake underneath in order to have a bit of a gap for the "grass. But you could also start with a 5" and then make a 2" ramp and an 8" cake. That would come closer to the servings she wants.

Carve it. 

 http://www.cakecentral.com/tutorial/20233/how-to-carve-a-spiral-cake

Thank you! :)