Idly batter: You need to use the same cup for all the measurement. Soak separately the rice and urad daal with methi seeds for minimum 5 to 6 hours preferably overnight.
Grind to a smooth batter and add some required salt. Transfer to a container. Allow to ferment. The batter will raise automatically once it starts fermenting. This takes 4 to 6 hours.
For the Idli podi: Dry roast all the above ingredients separately except salt and hing. For red Chilli add one tbsp oil for crispy fry. Let it all cool down. In a blender put all the ingredients with some salt and hing.
Grind it coarsely. Keep open for 15 minutes to dry a little and then put it in an airtight box for it to retain its freshness.
Take 2 tbsp of idli podi, make a well and add 2 tsp of regular cooking oil or gingely oil. Mix well with a spoon or with your fingertips. Apply this paste on both the sides of the idlies and keep aside for at least 1 hour.
Serve as it is or add a tadka on top and serve hot.