Just reusing a box I got in the mail now used to hold MY mail. Recycling! :)
Only tools you'll need are:
A craft knife
Some tape, I used parcel tape (Ironic yes?)
and some blu tak, or double sided tape, or just about anything you can think of to stick it to the wall.
Step 1: Step 1
First step is to cut the box in half, going in parallel with the folds on the bottom.
Then slide the two halfs into each other.
You should end up with something like this^
Step 2: Step 2
Then use the tape so that the two halves don't fall out of each other, I used some on the sides coming from the inside and a bit on the bottom going out to the back, as seen above
The last step is to add the blu tak, and stick it to the wall the you're all done!