Actually, I have two questions about an 11x15 cake. When making that size cake, do most people just cover it with frosting, etc. or do you tort it? Or, do you make two and stack them. 
Also, how much would one charge?
Any suggestions are greatly appreciated!
I'm at the lower end of the pricing scale from what I've seen, but I charge around $27 for an 11X15" (the 2" pan size) and usually don't torte. If they want a double layer I charge $40. If there's extensive design I add a few dollars. Doubling a sheetcake amounts to A LOT of cake and I haven't had a lot of requests for it. 
hun, you can do whatever you want with it (as long as it's legal LOL) you can torte it cover it with fondant or frosting, stack them..... carve them into unique shapes........ the list can go on.
O and BTW, the only silly question is one that isn't asked.
Welcome to C.C.
As for the charging part you can get away with at least 30 bucks for one of those. Walmart sells theirs for 21.87 so don't feel bashful about charging at least 10-15 more for yours. (besides we get ours frozen, you will probably make yours at home) So more lovin from the oven is there.
I look at pricing this way, you can always come down on a price but it's next to impossible to up.
Thanks everyone for your help. It really would make for a lot of cake by stacking it (ha ha).
I actually charged $40 for a cake I did last month for that size but it had about 20 flowers that I did ahead of time. It took about 2 hours just to do the flowers. That isn't too high is it?
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