Here is how I built a raised garden bed for my community garden plot.

I am replacing a raised garden bed at the community garden that has rotted out. The boards are 2' x 8" x 12'. I cut the boards to 3' x 6'. Since it's the community garden I am going very simple. Boards and screws. Nothing special. The screws are 2.5 inches but 3 inches probably would have been a bit better.