Rotten flax is made by floating a bundle of flax in a body of water or in a tub. Rotten flax can be dried on a drying rack or flax hammock. Also, rotten flax can be separated on a flax comb or hackling rake into straw, tow, and lint. In order to rot flax, you need to have the flax processing skill from the school of arts & music. Then you go to a body of water, click yourself, click special, then rot flax in water. If you click rot all flax, all the flax in your inventory will be rotted. Flax rots at a 1 to 1 ratio. Also, 1 flax takes as much time as 100 flax when rotting (about 20 minutes).