I had brought home some remnant 6x6 lumber from work that I had planned to use for firewood. However the cold snap we were in gave way to some rather nice Oregon spring weather and I decided I could find a more useful purpose for the 6"x6"x2' block.
-Fire-specifically embers/coals from a fire.
-A block of wood-end use in this case is a small strawberry garden.
-Tongs or other ember transporting tool. (I used 12" salad tongs). A scoop of some kind would probably work too.
-A scraping implement. I used a 2" putty knife.
-Appropriate PPE: gloves, long sleeve shirt, safety glasses, and a bandanna/respiratory mask.
*THIS METHOD USES FIRE: USE EXTREME CAUTION*
Step 1: Hollowing
First I should apologize for my lack of photography. I didn't discover instructables until after I was nearly finished with this project.
At first I tried using rocks heated in a fire to burn away the portion of the lumber that I wanted gone... For some reason I thought this would be an efficient method but I found that the heat just made the rocks break apart when I tried to retrieve them from the embers. The embers themselves worked marvelously for burning out the form of the basin but as one can imagine, I had to keep a close eye on them...especially once I added the fan (a small battery powered camping fan) which helped the embers stay hotter longer but also required increased vigilance on my part.
Once the embers burn out or cool off, use the scraping implement to remove the burnt portion until you get to solid wood again, then repeat the process of burning/scraping until you have achieved your desired depth. The bandana makes an excellent piece of respiratory protective equipment, though if you have a breathing mask, that would probably preferable...I learned that sneezing the soot back out takes much longer than simply keeping it out in the first place...gloves also help at this point too.
Step 2: Plant Plants...
Once desired depth has been reached, add dirt and desired vegetation...you're done!