I know the guideline for making a cake in a 12x18x2" inch pan is to use 3 cake mixes/triple a recipe. 

What I'm confused about is what this is meant to be- 1 single layer and for that to be the only layer of the cake? To be torted to make 2 layers? Or are you "supposed" to bake 2 of these to stack and make a 2 layer cake?

I have baked a few 12x18x2" cakes and used a different approach each time, but haven't seemed to get it just right yet.

When I baked 2 separate cakes and stacked them I would say it was too big/high.

I've torted the cake but the layers were a little too thin and very fragile for separating the layers, filling, and placing the top layer back on. 

One time I baked 2 separate cakes with 1.5 recipes of batter each but once again they were a little too thin and 1 layer baked very unevenly- one end was about 1/2" thick while the other end was closer to 1" thick. 

I appreciate any suggestions and feedback. Thanks!