Okay, so I had a cardboard box laying around, slightly larger than my phone (Xperia Z). I was thinking what should be done. Light-bulb [Mr.Gru in Despicable Me]. A charging pod so that my phone can sit on the wall plug without laying long messy cable to the nearest table or floor. Or what if your cable is not long enough from the wall plug to the floor? Would you hang your phone there? Disaster.

While thinking of the design, I figured out that I can even use it as a container for my travel charger, so I won't have messy cable in my bag no more. What a bonus.

All we need is an appropriate box, a cutter, and a ruler. Let's take a look...

Step 1: Charger Head Thickness

Firstly we need to measure the thickness of our charger, one inch in my case. Please don't ask why I have Samsung travel charger while my phone is Xperia Z. Because my stock charger is used at home on another project : DIY Sony Xperia Z Desktop Charger. So, this is what I had in hand in making this project :D
Now we draw a line mark one inch from the bottom of the box, and one inch from the back of the box.
Then cut it out with a cutter.

So this is what we have on this step.

Step 2: The Lid

Measure the bottom of the box marked with "X". Then measure X length to the top. So the vertical size from bottom will be : 1" + X + 1". You can now cut off the rest.

I cut off a little from top [photo #3], use it as a ruler to lightly cut a line where we will fold it later [photo #4]. Make a light cut so that it is easier to fold. Remember : LIGHT CUT not CUT OFF :)

Now we have this on this step :

Step 3: The Side Fold

Photo #1 : Measure one inch on the yellow lines, then LIGHT CUT the diagonal.

Photo #2 : Red lines are the folding lines. I LIGHT CUT the bottom line from the inside.

Photo #3 : You can fold it inside or outside, so the folding diagonal lines and bottom lines should one be LIGHT CUT from the inside and the other from the outside.

Step 4: Plug Hole

Draw a hole with your travel charger plug. Then make it slimmer because we don't want the entire plug go through the hole. Somehow the USB cable will hold the box in position anyway, so don't be afraid if you cut the hole a little loose.

I leave the top line uncut (I fold it) so that there will be no open hole when I use it as my charger box as you can see in photo #4.

Step 5: Humpty Dumpty Sat on the Wall

We are done. Give it a try.

Step 6: Bonus

As a bonus, now there's no messy cable in my bag. I just use a rubber band to hold the box. I was thinking of a magnetic seal around the box but that will be done later, when I have a broken tablet's case with small magnet in it :D