Talking from Robc's technique for backgrounds I decided to make my own bark, tired of bringing in bark from outside and even after cooking you get molds eventually, cork bark is too $$$$. I used 1" foam and initially cut the groves with a razor knife then used a dremel with a brush to clean them up and add more texture, took about 1/2hr to make, will make more and get better at the design. I first used peat then finished with a cactus soil mix to fill in the small crevices.