What is typically used in a sump pump crock to support a pedistal type sump pump?

It is an old cement crock, and there is sediment on the bottom. The old pedestal sump pump was sitting on two bricks on top of the sediment. I cannot get these two bricks to lay flat. Therefore, the pump is not as stable as I would like it. It doesn't seem to walk (move) when it runs, but I would like to know if there is a typical way to brace the pump in the crock.