Concrete Conundrum.

We've been landscaping.

What looked like this:

Now looks like this:

On the upper area where there is currently sand, we want to do something like this:

Big, simple plain slabs of concrete...even bigger than above, with gravel and plants between them. (and more plants than above) The sand is already in place for pouring it.

We can't seem to find anyone that could do a small concrete job like this, and do it well.

Any suggestions?