Preheat the oven to 425°F and generously coat two baking sheets with olive oil so the potatoes crisp properly during roasting.
Place the potatoes in a large pot with 1 tsp salt and enough water to cover them, then bring to a boil and cook until they are fork-tender but not falling apart.
Drain the potatoes and let them cool slightly so they are easier to handle without breaking when smashed.
Place each potato onto the prepared baking sheets and use the back of a measuring cup to gently press them down to about 1/4-inch thickness.
Drizzle the potatoes with olive oil and evenly sprinkle garlic powder, onion powder, remaining salt, and black pepper over the top.
Roast the potatoes in the oven until they turn golden brown and crisp around the edges, rotating the pans halfway for even cooking.
Remove from the oven and finish with fresh herbs, flaky sea salt, and Parmesan if desired before serving immediately.