yes they are right, i used stove and cook with claypot like this
nowadays no one really use charcoal stove.
this is how i do it
soak the herbs for 30 mins first, then cook with high heat till boil which take about 2 mins then switch to small fire / heat to boil for around 45 mins.
i will check @ 30 mins to ensure the water level is equal to more than one boil and let it boil till one bowl
then the 2nd days, just put 2.5 bowls of water to boil for about 30 mins
same procedure, high heat bowl till boil and turn to small heat to brew for 30 mins
alternative you can buy those herb pot which cost around 70 bucks, it auto brew the herbs for you...