I need to make a baby block (cube) cake big enough to feed 50 people. I figure a 10 inch square, 5 layer high should be enough. Do I put it together as if it were a wedding cake? Any pointers?

I would dowel and board every 4" of cake. Sounds like a big cake. Make sure you post a pic.

That's huge. Have you considered doing several small cubes? I usually do 4" cubes.