Prick the potatoes a few times with a fork, and cook in the microwave until they're fairly soft. Cut them in half, and allow to cool for at least 5 minutes. Then, grate or mash the potato flesh - you may want to remove the skins first (if you choose to grate the potatoes, the skin should fall away as you grate).
Add the grated or mashed potato to a large bowl, and add the flour, garlic powder, and a generous amount of salt and pepper.
Drizzle or spray some cooking oil into a waffle maker, and distribute the potato mixture into two waffles. Add a little more oil on top. Close the lid, and cook until the waffles are cooked to your liking (around 5-10 minutes).