I had the experience of designing and creating a raised bed backyard garden last week. For part of it we removed the sod, and double dug as best as we could (tree roots made it difficult) using a D handled spade and garden fork. Double digging loosens the soil to a good depth without mixing the top layer of soil with the deeper soil. This is important as different soil microorganisms prefer to live in different depths. We decided to put root crops in the section we double dug.
For the other sections we layed down a layer of cardboard over the sod. The neighbor was cutting down a birch tree as we were creating the garden, and these beautiful birch logs made a perfect border for the garden. Once we arranged the logs we soaked the cardboard with water for a good while, then spread an inch or so of sheep manure across the bottom layer of the garden before filling it up with soil. We used about twenty 25L bags of black earth soil.
A recently cut tree on the front lawn was a resource for mulch which we spread in the centre area of the garden and around the edges. Aesthetically I think the garden is quite striking.
The "U" shaped design faces south. Taller crops can be grown on the north edge. Around the centre of the "U" we seeded salad greens, for easy access. We seeded peas, chard, beets, carrots, spinach, arugula, salad greens, and transplanted some kale, new zealand spinach, and leeks I had grown indoors, as well as chives from my backyard garden. I'm excited to see how this garden transforms over the summer!