Is it necessary to use dowels and a separator plate for a 2-layer 6" cake that will be placed on top of a 3" high 11x15 cake?
Are you travelling with it? And how long will the cake sit on top of the 11x15?
I would think it would be ok if it just sat there for an hour or something... and if you keep them in separate boxes.
Someone else can probably answer your question, better than I can. Goodluck.
Welcome to CC!
Yes, I would dowel it, better safe than sorry. I foil cover my dowels so the wood never touches my cake