Kusamono is not really something which has caught on in a big way in South Africa, to my knowledge, but it is actually an art form which has developed alongside bonsai for many years, at least in Japan.
It is essentially a planting which may consist of anything including grasses or flowers. The material used in Kusamono plantings are often free; you can collect them growing just about anywhere if you go for a walk. You may find many of the plants suited to these plantings are even considered weeds!
As an accent plant when displaying bonsai, kusamono will often express the season. For example you might use a creeper with leaves which are coloured in the hues of autumn.
Alternatively kusamono will represent or exemplify a surrounding or habitat to the bonsai its an accent for; as an example you might use a compact growing, smaller leafed ground cover as an accent to a literati bonsai which will further enhance the idea of a rugged landscape.
A lot of fun can be had with the choice of container used to plant your kusamono into. As the container is generally quite small it is quite normal to use bolder coloured glazes, containers with patterns or drawings on and even more adventurous shapes. You can view an assortment of glazed containers suitable for kusamono as well as these unglazed containers.
You can use just about anything to grow your kusamono in, however you should remember that as the container is rather small and sometimes many plants are tightly growing in it you should try to use as little inorganic material (eg stone) as possible as this will further reduce the available space for the roots to grow. From what I have seen, Akadama is by far the most recommended medium to grow kusamono in as it is free draining but at the same time rather water retentive. It has a good CEC value, which essentially means it is able to retain much of the nutrients you feed to your plants and make them available to them over an extended period of time. Very importantly every available mm of the container can be filled with roots as the roots are able to penetrate the akadama. Read more about akadama here.
Kusamono are never placed directly on the surface of a table or surface. They are always positioned onto a wooden display table but more often onto a wooden board which is called a "Jiita." Take a look at one of a kind "Jiita," from the Garden Route in the Western Cape.
Here are a few of my favourite examples of Kusamono as photographed at the WBFF Convention in Saitama, Japan, 2017: