Weigh the dextrin and mix it with water.
Put the mixture in a double boiler cooking pot. With medium heat mix it until it thickens without boiling it.
Put the dextrin mixture in a hermetically sealed container until it cools.
Once the dextrin mixture is ready, mix it with the sawdust. Pour the mixture into a flat-bottomed mold.
Drying time depends on the ventilation of the mold and the temperature and humidity of the place.