To make it easier for the haulers, I sort my flattened cardboard boxes by size, and then insert the smaller ones within the larger ones, rotated 90 degrees. That way, they can grab larger bundles at once.
To me, this is less effort than the Japanese approach of using twine to tie bundles of cardboard together.
I live in Japan but all I do is get one big box, and then flatten all the others and insert them upright in the one lone box.
I do bundle them at work thought. And it also depends on the municipality how you should deal with them.