Add warm water slowly into the flour and bring the flour together - you may not need the whole water. Just ensure that all the flour is moist and the dough sticks together. No need to knead.
Boil water in your idli steamer. Grease the idli thattu.
Take a portion of the dough and push into a press with the thin hole disc at the bottom. Close and push through the top into each hole to make a small round. Sprinkle coconut if using.
Steam inside the idli steamer for 10 minutes. Take out into a hot pot.
Serve hot with curry of choice, or just with sugar and boiled plantains!
Notes
You could steam it as one big round too. In a usual steamer pan, line with foil or banana leaf, grease with coconut oil, and just round it in one big round. Sprinkle with coconut and steam till done.