Double digging is easy, all you need is a spade or shovel, a spade fork, and some muscle.
First, mark the area where your elevated plot will be situated. Loosen the soil with your spade fork by pushing it into the soil and moving the handle forward and backwards.
With your spade move the top 8 inches of soil from one side to the other side (just look at the picture and maybe you’ll get what I’m trying to say) J
Note: the picture above shows mung beans (green manure) being incorporated into the soil.
Now, loosen the bottom 8 inches of your plot (again, look at the picture). Do not mix the topsoil with the subsoil. Just loosen the subsoil.
Do this over and over and over until you reach the end of your plot.
I hope you got that. Some people have a hard time putting words into action. Me, I’m having trouble putting action into words… :)