I have 4 of these boxes that I am using for the square foot gardening method. Heres how I build them.
I normally use 1x8x8 untreated boards but for this box I got 2x8x8. Dont ask me why cuz I dont know. Anyway get 2 of these boards and get the people at Lowes or Home Depot to cut them in half so they will be 4 feet long. Then simply hammer in nails on each corner. I didnt take a pic of that sorry.
Then I laid down some weed paper so that the grass and weeds will not grow up thru your box. You can also use layers of newspaper or cardboard. If you use cardboard layers, wet them really well.
After this I filled the box with the soil. For this box I used (6) .75 cubic feet bags of Scotts top soil and (2) 1 cubic foot bags of mushroom compost and 1 bag of Scotts humus and manure soil amendment. This came in a brick and it looks like clay. Heres what it looked like after I broke it us with my shovel for a bit.
I ket breaking up the humus and manure and mixing it in well with the other soil. Now its time to make the grids. Most people use wood beams to make thier grid lines but Im cheap so I use twine. I take a ruler and measure 1 foot and make a mark where the nails will go all around the box. There will be 3 nails on each side. I only drive the nails in half way and then wrap the twine around the nail and tie a knot like this.
Once this is done all you have to do to secure it is finish hammering the nail all the way in so it will secure the knot in the twine.
Repeat this with the nail on the opposite nail on the opposite board until you have made a grid of 16 squares in the raised bed. It should look like this once you finish. The twine is purple so it may be hard to see but over time it will lighten up.
It took about an hour or so to build this. Its easy! You can do it!