Get four different colors of brown polymer clay, preferably dark brown, brown, light brown, and cream. These colors can vary depending on the type of look you're going for.
Roll out each color into a cane (or worm as they called it when you were little).
Put the four pieces together into one large cane and gently twist until it looks like the image. Roll it into a tight cane.
Roll, stretch fold, roll, stretch, fold, etc. until the woodgrain is the desired appearance for your project.
Use a pasta machine or rolling pin to roll the cane into a plank of "wood".
Use your woodgrain canes and planks in various projects. Bake at 275 degrees Fahrenheit for 20 minutes per 6mm of thickness.