I was browsing the web on gardening and come across this amazing soil cube tool. I really like it but it probably costs about $50 if I have it shipped to me in Shanghai and would take a few weeks. I end up fire up SketchUp, do a quick design and in two hours, I have a DIY soil tool and making cube! Totally awesome! The source can be downloaded here.
Soil Cube Tool
3D Printed Version