Requires only Cardboard, scissors (or knife) , ruler and any kind of Tape.
Step 1: The Structure
Crease your card like so in the picture. Then trace out your box. You can have it any length but make sure height wise, you have four creases in it.
Step 2: Cutting the Structure
Self explanatory... Cut it out with scissors or a knife. Don't cut the creases out! When done fold together to see if the fit is firm and tight when folded.
Step 3: Extra Supports
Cut two squares out that are the same height and width as the box. Attach them in the box as shown in the picture. This can be fiddly and i recommended you do this once at a time.
Step 4: Done!
Done! You can make it look even better by painting it or removing the hollowness (is that even a word) . You can even put a little bank to one side like shown in the picture!