Wash the rice well atleast 3-5 times and then soak in excess water for about 4 hours.Add the fenugreek to soak along with the rice.
Wash the urad dal 3-5 times and soak that separately for 2-3 hours
Soak the aval ( rice flakes ) separately for 2 hours.
Drain most of the soaking water ( keep the Urad dal soaking water) and keep the rice and dal ready. Keep it covered.
After the soaking time, grind the urad dal till it is soft, smooth and fluffy.
Add just enough water to get it to a fluffy batter as you go. Use the water from soaking as it gives the necessary stickiness to the overall batter.
Remove the urad dal batter and grind the rice with the fenugreek to a smooth batter.
Use water as needed to help the grinding.
When it is nearly getting done add the soaked aval ( poha) and grind to a smooth paste.
Once fully ground, remove this batter and add to the urad dal batter.
Mix the two batters really well with the salt added.
Store the batter in a warm place in your kitchen, away from direct heat / sunlight for about 8 hours to allow it to ferment.
Check the recipe notes if you are in a cooler place or if it is winter to see how you can ferment the batter.
Once fermented the batter will rise considerbly.
Once risen the batter is ready to make the dosa.