The depth of the raised bed can be anywhere from 8" high on up. Typically, if your soil is hard and compact then you will want a deeper bed so you can control the soil and have a nice workable garden that drains well.
Start with your four posts, panels. These can be boards or garden poles or blocks. Make sure the wood is not treated wood to prevent any chemicals from seeping into your vegetables if it is a vegetable garden. The length is up to you also. You can stack several of the garden poles on the flat edge for a higher bed. If you are using blocks, then stack them as high as you want, typically 2-4 courses. You can also use 4 x 6 and only use one board per side. Nail or screw the lumber into corner posts posts to form the corners of the frame. These are square corner posts that are cut to the height of the bed. Use galvanized nails or screws. Nails are easier and faster, while screws are stronger and more durable.
Dig a small trench 1 to 2" deep where the boards will be places. Position the frame in the trench. Level it by either adding soil or digging a deeper trench.
The final step is to add plants. Get creative with plant material and vegetables and have fun. If you want to build your planter with block or are looking for help with your raised planting bed, contact Arizona Living Landscape & Design for help. 480-390-4477 www.LandscapeArizona.com