I started by prepping the box with some painter tape around areas of the box that will be cut. The reason for this is to have a surface that can easily be marked on, but it also prevents the stickers on the box to stay in place and not be ripped when being cut.

After placing the painters tape, use a ruler and some simple math to find the center of the cigar box, and use the dimensions of the neck width to determine how much to cut. Repeat the process on the other side of the box.

If you are uncertain of your measurements, you should try and re-measure until you are certain. Remember that if you cut too much, there is no going back or a redo. If you cut less, you can always sand or file away more to get parts to fit properly.