Combine salt and roasted rice flour. Add boiling water gradually and using a wooden spatula mix the dough. Add water till the dough comes together. Using your hands (be careful the dough can be very hot), knead together until you get a smooth and soft dough. The dough should not be too tight and it should not be sticky also. Cover the dough with a wet cloth.
Grease the top and bottom of idli moulds (refer notes). Sprinkle the grated coconut on these moulds.Take small portions of dough and press each portion through Idiyappam mould or Idiyappam presser onto greased idli moulds or banana leaves.
Once the water starts boiling in the steamer, place the idli moulds and steam for 7-9 mins on medium - high flame. Keep the steamed closed for a min or two. Transfer the cooked Idiyappam to a serving plate. Serve hot with any curry of your choice.