Granulated cork is used to make insulation corkboard.
Ground cork is put into a mold that is put into an autoclave (a big pressure cooker) and steam baked at a temperature of 300 degrees centigrade (572 degrees Fahrenheit), with no contact with air. The natural resins in the cork liquify and upon cooling, the mass solidifies. Afterwards, the blocks are cut to the desired dimensions.
Insulation cork density is usually 7 pounds per cubic foot, however, for duck decoys, 9 pound density is used.