Heat the avocado oil in a large pan over medium heat.
Add the cumin seeds, fenugreek seeds, fennel seeds, and mustard seeds. Allow them to splutter and release their aromas. This should take about 1-2 minutes.
Add the thinly sliced potatoes to the pan. Stir well to coat the potatoes with the aromatic spices and oil.
Sprinkle the red pepper flakes, turmeric powder, and salt over the potatoes. Stir to evenly distribute the spices.
Pour in the 1/2 cup of water and give it a gentle stir. Reduce the heat to low, cover the pan with a lid, and let the potatoes simmer for about 20-25 minutes. Stir occasionally and add more water if needed to prevent sticking.
Check the potatoes for doneness. They should be soft and mushy. If they're not done yet, continue to simmer for a few more minutes.
Once the Achari Aloo is ready, remove it from the heat. Serve hot with plain steamed rice.