Spread white chocolate on a sheet of acetate in a layer about 1/16-inch thick. Drag a cake comb through the chocolate to create alternating lines. Return the excess chocolate to the bowl. When the chocolate stripes are firm but not hard, use an offset spatula to spread a 1/8-inch thick layer of dark chocolate over the white chocolate. Let the dark chocolate set until firm but not hard, then place a piece of parchment paper on top of the chocolate. Pick up the plastic by a corner and carefully wrap it around any tube. Secure the plastic closed with tape and place in the refrigerator.
Place a piece of bubble wrap, bubble side up on your work surface. Randomly drizzle white and dark chocolate onto the plastic. Use an offset spatula to spread the chocolate in an even layer to create a marbled effect. Place the plastic in the refrigerator.
Spread some white chocolate onto a sheet of acetate. Pull a wood grain tool through the chocolate to create a wood grain design. Let the chocolate set slightly, until firm but not hard. Cover the design with dark chocolate and use a spatula to gently spread it into layer that is about 1/8-inch thick on one end and graduates to a 1/4-inch thick at the other end. Let the chocolate set until firm yet pliable but not hard and set it inside a tall round container. Place it in the refrigerator.
Cover a piece of textured plastic with about 1/4-inch thick layer of chocolate to create any desired size and place in the refrigerator.
To unmold all of the chocolate pieces, remove them from the refrigerator and just gently peel away the plastic. Keep the unmolded pieces in the refrigerator until you are ready to put the sculpture together. Use the melted chocolate to "glue" the pieces together. Arrange the chocolate pieces as if you were arranging flowers of different varieties. Let your natural artistic eye guide you in the design.