I save my empty laundry detergent boxes to make cheap magazine holders. They can be cut on an angle like the ones seen in office supply stores or just left uncut. I then spray paint them or cover with contact paper and plop my magazines inside.
That sounds like a good idea. However, if one has a well, liquid detergent should be used. Powder detergent is very hard on a septic tank. If I had city water, I would certainly be using your idea.