Everyone seems to spend a lot of time carving round cakes or something, I highly recommend using the Wilton football cake pan - make 2 cakes and put them together, then simply notch the edges!
The secret to getting this Roasted Turkey Cake just right was a 4 day process - day four, fondant cranberries and leaves. (My leaves look fake and next time I will go for a less perfect shape and a more sage color.) Cranberries are easy. Day three, rice krispie drumsticks and wings. I coated the bone tips in white chocolate, but I'm sure frosting would do on day one. (Store them in an airtight baggie till you frost them on day one.) Day two, bake the cakes. And on day one, put it together and make the stuffing.
I tried to make the stuffing early, and it dries out - gross. Make it that day. Simply use a half sheet pan so the cake is very thin (or bake half a cake mix at a time in a 1/4 sheet)and you get lots of good brown edges - use a yellow cake mix. Afterwards I simply cut it into squares, mixed the cubes around in the pan, and then while it was still in the pan, used a basting brush dipped in green food color and very gently dragged over the edge of the bowl to speckle on the pan of cut stuffing - looked like oregano and seasonings.
Then just frost the cake, (I used homemade buttercream), frost the legs and wings, and attach them. (I had shaped them so they stayed stuck to the sides, but you could use a candy stick if you need to anchor them.)
The next secret is the airbrush; to be honest, it makes every mistake look fantastic. And there are imperfections in the surfaces of food so this project is very forgiving. If you don't have an airbrush, maybe you can find the food mists in brown? Be sure to make the creases and underside darker for added dimension. (If you are an aspiring cake decorator, get an airbrush. You can find a small one on eBay and it's plenty affordable and absolutely essential.
I am a cake decorator at a local supermarket with a big airbrush and you don't need the big one.)