Lego Block Cake

This is Conner's 4th birthday cake. He's big into building blocks and loved the idea of a blocks cake. It was made from a 9x13 and 9x9 cake cut into smaller pieces. The little circles on the top are made from marshmallows cut in half. I thought this would be an easy cake to make, but cutting the cakes apart made them crumbly and hard to ice. Perhaps freezing (as someone had suggested) would have helped. Live and learn!