I believe it takes time and a little trial and error to get it exactly right. The heel on the pedal method provides a useful starting point but from my own observation of other cyclists, some pedal toe down and others pedal with their feet basically level with the ground. This would have an effect on ideal saddle height, as will the fore and aft position. Don't play with the fore and aft position to change the reach to the bars, change the stem if necessary.
The knee over pedal spindle method of setting the fore/aft position of the saddle works perfectly for me, although many others say it has no basis in fact, but again it is a useful starting point. Alternatively, try the traditional advice of having the nose of the saddle 2 - 3" behind the bottom bracket spindle.
I have also seen it suggested that the straight leg with heel on pedal advice originated in the 1920s, when cycle shoes didn't have raised heels, just a flat leather sole, so doing it that way with a shoe with raised heels can leave it ~1/2" too high.
Unless you have a bike with very relaxed frame geometry and low bottom bracket height, you will not be able to put your feet on the ground when stopped. If you can, it is definitely too low.