All-and-all, this cinder block raised bed system is really a great idea for a multitude of reasons.
You begin by, digging out your garden bed area and stacking your cinder blocks in a rectangle.
Then you lay out the plastic at the bottom of the bed and fill with organic topsoil.

Image By: Vermibag Composting & Gardening Systems
This is one of the best gardening ideas I have ever found!

