After several years of gardening, I came across this photo online of whats called a “keyhole design” raised bed (since it looks like a key-hole from above) and is very popular in Africa.  Basically the concept is to combine your composting and raised bed in one…with compost bin in the center to “feed” the veggies when it rains and the goodies leech out the bottom.  Much smarter to actually be able to “use” the run-off then waste it in the grass in the back of the garden where the compost bins usually are located.  Sounded smart to me, so I built both a brick and wood version.  The wood is cedar pickets which is faster and easier to construct over laying a concrete footer and laying brick.  (I like the brick better though).  The photo I got the idea from had the center compost bin very small (too small in my opinion) so I built mine the same size as my other compost bins in the back of the garden.  The compost bin size needs to be a min of 3 ft x 3ft to contain enough “mass” to produce the heat with the microbes consuming the material.

So with the center being 3′ x 3′, I added about 20-24 inches to the outside wall…so the total size is about 8 ft x 8 ft.  You leave the “pathway” to the center accessible so you can turn the pile and empty the pile when its ready.  The wood version has holes drilled in the bottom 2 boards to allow worms and nutrients to pass back and forth.  In the photos with the brick version, I will be building 2 more behind those and wood chip paths in between.