Corkbark can be bought in most local aqua shops around. Remember that corkbark will float and soaking it will not solve the problem, it will float anyway. An aquastabil aquarium or a similar tank have an aluminum edge at the top. Then the corkbark fits nicely under this edge, and will stay there. If you have an all glass tank, a good way is to attach the corkbark with the use of silicone.
Next step is to attach plants.
Species like Vesicularia dubyana, Micrsorum pteropus, Anubias spec, Bolbitis heudelotii and even Riccia fluitans can be used. Remember its easier to attach them before putting the corkbark in place. If you already have siliconed the cork in the wall, you can also use small needles to attach plant with. Its even possible to take the piece of fishing line, put it around the plant and fasten the line in each side of the cork. The corkbark is now soaked and is rather soft, and this allows the fishing line to be pressed down into the soft cork.