It seems trivial, but i shall tell you how to cook potatoes.
Water from a tap
Potatoes (good, waxy or floury, both have their merrits in this)
Olive Oil, preferably mild, but any will do.
You shall peel them, and cut them in 1,5cm - 2cm cubes.
Then you shall boil them, in enough water to cover them, for 6 minutes since they start boiling (covered ; and salt the water generously, and put them together with the water from the tap, not after its started boiling).
Then, simply drain and cool them running the tap on them, like you d do with pasta, and smother them with some more salt and some light favoured olive oil, with your hands. Shuffle them around in a baking pan, the LOWEST rimmed pan, or just a flat open tray, use what is your most shallow, most open walled baking vessel whatsoever.
Shuffle well, as this releases the startchy flouriness around the potatoes, and the oil will rub into their edges with the salt.
You need enough oil to coat even a little tiny bit of all of them.
Wait 10 minutes, let them sit, they ll cool down and the oil will sink in a bit more.
Meanwhile put your oven at 220.
Stick in the oven, mid to low shelf, and leave there for 20 minutes. Check to see how crisp they get.
The floury texture soaked in oil just around the surface of the potato but still just steamed in the middle is a treat.
Elaborated simplicity part 1.