We purchased a kit of brackets from Lee Valley Tools, the green metallic items shown here. Then we screweed these onto two 2" by 4" frames of pressure treated lumber. The sides of 12" by 12" patio blocks were placed in the brackets of the lower frame, and then, after a great deal of effort, the upper frame was added for stability.
We plan to grow roses or another climbing plant from the lower garden level since this is the sunniest exposure. Herbs or vegetables are being considered for the raised section. The trellis will give a little more privacy to the patio area.