We suggest using a sheet of Melamine particle board, 3/8 or 1/2 (preferred) inch thick, commercial grade, from your lumber supplier. Ask for Melamine particle board finish, not to be confused with white spray-painted particle board. The Melamine particle board is exceptionally durable, resists scratching and staining, and easy to maintain and clean.
Measure the dimensions of your silicone mold, length, and width. In this example, our new silicone mold measures fifteen by thirteen inches. The Melamine board should be a couple of inches larger than the mold itself. In this example, our board would be seventeen by fifteen inches.
Check the level of this board and adjust using plastic or wooden shims. Leveling this board is easier than leveling a large working table. Spraying or spritzing water on the surface on the Melamine board will form an air lock when the silicone mold meets Melamine surface. Let the mold 'free-fall' onto the board -- do not touch or move -- as the silicone mold is in the correct alignment. If not, try again. You want to avoid the mold from 'snaking'. A helpful hint would be to run a true pencil line, one inch in on the length and width. Then position the silicone mold manually to meet the length of the mold along the pencil line. So, the same for the width.
Fill each mold cavity starting in a corner and continue filling until all twelve cavities are filled. After the soap bars have harden, we suggest gently pulling away the sides of the molds to break the air lock formed during the casting.
Finally, place a second Melamine board face down on top of the cast mold. Holding the bottom and top boards together with both hands, flip both boards together at the same time. Once the mold is upside down, remove the top board. Then slightly lift the mold to separate each soap bar as they release from the mold.