The idea is to fill the box 1 in the first season. The middle box is used for collecting and storing excess material. As the material in box 1 shrinks, refill it from box 2. The next year, fill the box 3 and use compost from the box 1. This way I don't have to turn the heaps, but only wait for compost to be ready.
So far, I made the two of the boxes. The old one, as seen in the photo, still contains some of the compost. I need to sift it and spread on the beds in the vegetable garden. It started to rain and I haven't finished the job.
The black plastic container which I got from our council (free) is used only as the storage for leaves. It is an important source of so-called 'brown material' which is usually in short supply when making the right compost mixture.
I also have two compost boxes made of wire mesh with wooden studs in the corners.