Brush or spray a generous amount of mold release into the mold, choosing the proper mold release for the materials you are using.
Bolt or strap the mold together, if it is a multiple piece mold.
Mix a small amount of tint into the silicone, if color is desired. Mix the silicone rubber components together in a bucket according to the directions.
Place the mold on the floor. Pour the silicone slowly into the mold, holding the mixing bucket as high as you can. This will cause any small bubbles to break as the silicone dribbles into the mold. Fill the mold to the top.
Remove the silicone from the mold once it has cured. Different silicones have different cure times, but you will know it is ready if it is not sticky to the touch.