Some of the hardest work we've done will never be seen by anyone. (I'm not complaining - it's just one of those things.) The grey water treatment from the outdoor kitchen sink is not a good example - it was really quite easy.
We took a (free) bath and put a load of washed gravel in it:
We laid some (found) weed matting on top:
Then some washed sand:
Some top soil:
And finally some mulch from the other side of the valley.
More mulch was added, and some plants. But you get the gist. Before it gets here, water drains from the sink, through some straw in a box, and along a pipe under the kitchen paving. (The kitchen paving - that was hard work.)