I make boxes for the items that I sell on eBay. Making an item's own box minimizes the size, the weight, the need for more packaging material, and thus making the postage/shipping fees less.
All you need is second hand cardboard, a box cutter (razor blade), and packing tape (in a dispenser works best).
Step 1: Break Down
Step 2: Mark the Corners
Do not cut away the cardboard to remove it at this line! Just make a mark with the blade that cuts the top surface of the cardboard! (Later we will see that this makes the cardboard fold perfectly.) Make another parallel cut line on the other side of the item. Then roll the item on its side so one side is still on the previous cut line, and make another parallel cut line while the item is at 90degrees in the air. Lay the item down to finish its 180degree roll, keep one side on the previous cut line, and make another parallel cut line on the edge that just touched down on the cardboard.
Now leave half the width of the item as space on the cardboard(like we did in the first cut line) and cut this remaining excess cardboard off completely, from top to bottom using the box cutter.
Step 3: Cut to Size
And leaving half the width of the item as extra cardboard on the opposite side, cut the rest of the excess cardboard off completely, from side to side.
Step 4: Flip & Fold
Place the item inside the box and fold shut. I wait to tape after I fix the sides, but for your first box it can be easier to tape the box now, where the edges meet from top to bottom.
Step 5: Fix the Sides
You should cut the exposed corners to make four individual tabs. Cut from the inside-out with the box cutter, starting at the item and cutting away from it. After you cut all four side corners like this, make four cut lines on the outside edge where the cardboard folds across the item. Repeat this process for the other side of the box.
Then you will be ready to tape the box. You can tape it all at once, or in pieces. It depends on how much tape you think your box needs- but a nice, fitting box that has been well cut just needs a line of tape around the sides where the edges meet.
Step 6: Ta Da!
If you have a fragile item, bubble wrap then a custom cardboard box works. You can also branch out and build boxes to fit other things, like making your own triangular box to fit posters, or an oblong or different shaped box to fit anything.
But that isn't all. You have saved money by using minimal tape, no packing peanuts or foam, and a cheaper postage/shipping rate if you are going to ship because of shipping in the smallest/lightest possible package. And to mention on top of that, you are recycling boxes by giving them a second life!