When making the 10mm scale hay stacks I had opened a pack of air drying clay I bought about 6 months ago, to keep the clay fresh I rapped it in cling film and put it into an air tight chines take out box, but the was quite a bit left over, so rather than let it go off and harden. On the spur of the moment I decided to have a go at some sand bags.
The water tower from my 15mm scale flying boat station was designed to have a sand bag bunker on the top. I rolled the clay out into sausages to the right size and then started to cut them up with a scalpel. It then struck me that rather than cutting right throw the clay, all I need to do was put the blade three quarters of the way through. Creating long lines of sand bags still attached to each other. Ready to use in future.