Use a sharp knife to peel the outer thick skin of cassava. Cut the cassava into about 4-inch long log. Half the log and then remove the tough core in the middle if you see any. Place the water and sugar into the pot
Place this in a medium/large saucepan and make sure you arrange them in one layer so they can cook evenly. Pour water and sugar. Make sure the water covers the cassava pieces
Bring to a boil and then lower the heat to a gentle simmer. Cover with a lid leaving it ajar a little bit. Cook for about 1 - 1 1/2 hours or until you see the cassava turns translucent and soft. Turning the cassava pieces halfway gently throughout the cooking time. By the end of cooking time, the cassava would have easily fallen apart if you poke with a fork. The sugar would have reduced to be pretty thick and gooey (because of the starch from cassava)
Prepare coconut sauce:
While the cassava is cooking, prepare the coconut sauce. Place the coconut milk, salt, and flour in a small sauce pan. Whisk to make sure the flour is mixed in and no lumps. Bring to a gentle simmer, do not boil. The sauce will thicken slightly.
Serve the cassava with some extra syrup drizzle on top if any left from the pot followed few drizzles of the coconut sauce