How to build a cheap raised garden bed

I’ve been advancing my guerilla gardening efforts recently, with a significant new raised bed now beautifying my nature strip, as seen in the featured picture. I thought in this post I could provide a brief overview of how to build a cheap raised bed, either for use on your nature strip or in your front or backyards. This overview might seem a bit basic for the handy builders among you, so I direct this post to those who are beginning their journey into guerilla gardening and urban agriculture.