You could make chicken gardens. Sorry I'm in the US and don't know the conversion to lumber you have available but...
A wood frame maybe 1/2m x 1m filled with soil and planted with greens covered with wire mesh. You could line the sunny side of the run. As the greens grow they poke through the wire allowing them to be eaten. The wire prevents the roots from being scratched up. There are posts on this site with better information. I'll see if I can find some later when I get home. Right now I'm at work.