Start with a small jar, such as a mustard or candle jar. Dissolve the appropriate amount of gelatine to fill the jar and set like a solid jelly. While it is still in liquid form but cooled and beginning to thicken, add 5ml of fragrance or essential oil and a couple of drops of food colouring. Allow to set. Cover the top with cling wrap and pierce it with a few holes. Place in the bathroom or toilet for instant freshness.