Getting to pack something very neatly and securely has always gotten people in trouble most especially when it turns out to be a flimsy one. The thing about cartons is the available thickness and rigidity which is often quite a headache to get hold of and does not cost most of us an arm and a leg. This is mostly experienced when we send of parcels by courier and we get to do the packing ourselves. Our recipients often comment that items get to their ends in bad condition.
I have had experience in the export business and I would have to say that making sure goods reach the clients’ end as secure as possible. What I used to do was to have the dimensions as accurate as possible then, with the existing material and just trim it down to its proper size. I would suggest using a Martor USA box cutter to make it as precise as possible.