I got my guys at work to knock together a box dim (80cm x 35cm x 43cm deep) out of some old left over planks we had lying around. The bottom has a nice 5cm gap along the entire length in the middle which provides great drainage.
I followed your instructions on how to go about layering the box and planted some seedlings a little bit haphazardly, but the lettuce is growing super, almost time for a taster. I just mixed it up with some spring onions, chives, parsley, basil, a tomato plant, and some marigolds to lure the bugs.
So far so good I will be planting some beetroot and radishes in the visible gap. The soil level is about 15cm below the top on the wooden box which has been a huge advantage protecting the young seedlings from the pretty harsh Cape winds which have been decimating some of my other herbs. Watering everyday is proving to be essential.
Will keep you posted on the first fresh homegrown salad from the balcony. The little seedlings have a great view of ³the mountain² from there 😉
PS Photos are pretty low res.