I have no idea what height that is, but basically the theory is that carrots are best put into raised containers to that they're protected from carrot fly. Plus, then you have better control over the type of soil they're grown in.
So, in the spirit of upcyling and preserving some of the history of our house, when we ripped out the old bathroom, we kept the old cast iron bath:
|We even kept the taps!|
For drainage, and so we didn't have to use a huge amount of topsoil to fill it, we put broken bricks in the bottom of the bath, covered them with sand, and then filled up with topsoil. In the first year we split it between salad greens and carrots, and the salad survived the Great Slug and Snail Massacre of 2012 completely untouched. But, we loved the carrots so much it's all carrots now.
Now, this thing is HEAVY. It's cast iron, filled with bricks, sand and soil. There was NO moving this thing. Until we realised that it was in the way of the forklift for our extension...
Fortunately, the guys doing our extension are awesome.