Bring a pot of water to the boil. Cook potatoes until soft, about 20 minutes. You can also microwave them.
Preheat oven to 375 degrees.
Drain potatoes and pat dry them.
Place on a greased baking dish and use a potato masher to mash down the potatoes, trying to keep them as one piece. The more you mash them down (the thinner they get), the crispier they will be.
Evenly spread the margarine across the potatoes. Sprinkle evenly with all of the seasonings.
Bake for about 40-45 minutes, until your desired crispness is reached. Do not flip the potatoes.