Heat your oven to 425°F before you do anything else. Brush two large baking sheets generously with olive oil while the potatoes boil. I skip parchment paper here, because the potatoes crisp best when they touch the oiled pan directly.
Place the potatoes and 1 teaspoon of salt in a large pot. Add enough water to cover them by about 1 inch, then bring it to a boil. Cook for 15 to 20 minutes, until they are soft and a fork slides in easily.
Pour the potatoes into a colander and let the steam escape for a few minutes. They should be cool enough to handle but still warm. I find that dry potatoes crisp up far better than wet ones.
Set each potato on the oiled baking sheet with a little space between them. Use the back of a flat measuring cup to press each one down gently. Aim for about ¼ inch thick, and press slowly so the edges stay in one piece.
Drizzle the smashed potatoes with olive oil so every surface gets coated. Sprinkle on the garlic powder, onion powder, remaining 1 teaspoon of salt, and pepper. I like to season generously here, because the seasoning bakes right into the crispy edges.
Slide both pans into the oven and roast for 25 to 35 minutes. Rotate the pans halfway through so both sheets brown evenly. You will know they are ready when the edges look deep golden and crunchy.
Taste one and add more salt if needed. Top with fresh herbs, a sprinkle of flaky salt, and Parmesan if you like. Serve right away while they are hot and crisp.