There are many ways to create raised beds. My favorite right now would be to use straw bales to create a rectangle, place a piece of cardboard in the bottom to suppress weeds (and prevent roots from accessing the soil before it is properly cleaned), then fill with soil. That would take a bit of organic soil, but we could put a few inches of wood chips in the bottom and make it even more rich. The soil can be half way up the bales. We will be putting mulch on top anyways (no exposed soil!). In the early spring and late fall an old window can be placed over the bales to create a simple cold frame. We can sit on the bales for ease of reaching. We are using a natural means of holding the soil in, and as it breaks down we just release the strings from the bales and blend it into the soil or use as mulch.
Old pieces of wood can be fastened together. Large scavenged rocks can be used to rim a garden as well. Our only limit is our creativity.
Large containers could be built to place on concrete. Small ones to be placed on a picnic table. Then, of course, the smaller of the raised beds is simply a pot! There are many ways to incorporate vegetables and fruits into the landscape.