This is something I spotted in BBC Gardners World magazine last year and it has taken until now to put it into practice. You can plant either herbs or salad leaves or a bit of both. We went with herbs and both Tom and Jack choose which ones to have (from a list) and sowed their own seeds which are all labeled in the photo here. The rules are simple, six rows well spaced out, no big plants that needs lots of root space or will take over the whole bag. Fantastic idea for cut and come again salad leaves and when the row gets too big or starts to go to seed you can just scoop that row out and then re-sow.
We may get a second bag for salad leaves which will then feature beetroots for their small leaves when still young and before the root have developed. Raddishes too might be an idea, sowing two rows a bit after each other in turn.