I am making a number 3 cake for a child's birthday. The "3" is about 2 1/2 ft from top to bottom so I have a huge number 3 that I am using as a template to cut the (sheet cakes) into a huge number 3. Normally I would use fondant to cover it and help hold the pieces together but this woman hates fondant.  My only other thought is to assemble the 3 and then pour ganache over the top. Will that keep the pieces from falling apart? Any other ideas?  Thanks very much!

I would think buttercream would work as well

crumb coat with BC, chill and frost. i never use fondant. it should be fine.