Rinse the flattened rice in water and soak it for 15-20 minutes.
Drain the water and transfer the flattened rice to a mixing bowl.
Add rice flour, urad dal flour, cumin seeds, green chili, asafoetida, and salt to the mixing bowl. Mix well.
Add enough water to make a thin batter. Mix well to remove any lumps.
Cover the bowl and let the batter rest for 4-5 hours or overnight.
Heat a non-stick tawa or griddle over medium heat.
Pour a ladleful of batter onto the tawa and spread it in a circular motion to form a thin dosa.
Drizzle oil around the edges of the dosa and cook until the underside turns golden brown and crispy.
Flip the dosa and cook for another minute or two.
Serve hot with chutney or any other accompaniment of your choice.