On a brasilian recycling website I found a good tutorial on how to make a box from PET bottles (click there on ‘Tutorial – How to make a square box’).
I won’t do this because we don’t buy so many PET bottles and if we do we can give them back.
But I think that the tutorial can be used with other materials, too, I will once take a look.
Links:
Utsumi – Crafts with PET plastic, click there on ‘Tutorial – How to make a square box’