How should I do a cake topper to resemble the one on this cake? Is it a half styrofoam ball or something else?
Are you talking about the flowers on top? I think it's just how far the flowers are pushed into the cake. You create the "dome" look by pushing in the edge flowers more than you did the middle ones. Or if you wanted to make a preassembled one to just sit on the top, then you would use the half styrofoam ball. I would cover the ball in some pretty fabric first though. You don't want to see ugly foam through the flowers.