Last second raise bed thoughts

[Zeus123]

Hey all,

Without providing too much background I recently moved into a new house and have all my tom's in containers. I have identified a potential raised 'emergency' bed for some slow growing plants and experimental suckers. How deep does a raised be really need to be for tom's? The picture below shows what I have to work with. The sand on top is the easiest part. Below it is the hardest clay soil mixed with the strangest old housing debris I have come across. Think of digging into clay and reaching an old wood foundation 2 inches in. What would you do with this area? Again this is more or less for a couple plants that didn't make the cut, but I would still like to play around with.

Thanks,

Zeus