Making a custom box can be used for a few good reasons that I have found, as well as- I'm sure it could be used for various other and different reasons. Maybe it is a holiday season and you are wrapping a gift that needs a box for shape or structure; or would benefit from a layer of protecting cardboard; or need to fit an item of an odd shape/size into a box for storing/mailing.
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
Break the box down starting with opening the tabs on top and bottom of the box. Just unfold the tabs, or cut through the tape with the box cutter and then unfold the tabs. Lay the box down on its side and cut one of the corners from top to bottom so that you can unfold the cardboard once more to end up with a long, straight piece of cardboard.
Step 2: Mark the Corners
Now there is one long piece of cardboard laid on the floor. Place the item(in this case- a framed picture) on the cardboard where half the width of the item is equal to the space between the item and the edge of the cardboard. (So if you were to fold the cardboard up on the item, it would only be halfway across that side.) From top to bottom, cut very lightly with the box cutter to draw a cut line into the cardboard at the place the item's edge meets the cardboard.
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
Now, push the item towards the top or bottom of the cardboard so you can cut it down to size. Do not push the item to the exact edge! You will need to leave half the width of the item's side as extra cardboard that will be able to fold up onto the sides of the item.
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
Now, take the item off the cardboard and flip the cardboard over onto its other side. Fold along the cut lines and see how easily and perfectly it bends and forms the four corners of the box!
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
Now, look at one of the two open sides and you will see your item's side and some excess cardboard hangover. This is what will be used to fold over to form the side of the box.
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!
You have made a box!
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!