Use a starchy potato like Yukon gold so that the inside of the potatoes will become fluffy and tender when roasted.
Place the peeled potatoes in a large bowl of cold water to prevent them from turning brown.
You don't want to overload your baking dish because then the potatoes will boil instead of bake.
Greek potatoes will likely need about 40-45 minutes to bake, but keep an eye on them in the oven, so they don't burn. If you'd like them crispier, you can broil the potatoes for 5-10 minutes on the upper rack.