Is there more fibre in the paper box or a serving of corn flakes?

The box. The box could probably count as fiber, since it is undigestable plant material. However, it isn't a food item per-se. Anyway, there are many cereals with more fiber than corn flakes. The older I get, the more tempting that box gets.
Yes. You mean the fiber in the box that hold corn flakes than the fiber in the corn flakes, then weight per weight yes. Edible boxes are not made yet!