Bring a medium pot of water to a boil, then add 1 tablespoon of kosher salt and the potatoes. Cook for 20–25 minutes, until the potatoes are fork-tender. Drain the potatoes in a colander and let cool for 5 minutes, or until safe to handle.
Preheat the oven to 400°F (200°C)..
Transfer the potatoes to a baking sheet and smash using the bottom of a cup or a fork to about ¼ inch thick. Arrange the smashed potatoes in a single layer, then drizzle with the olive oil and season with salt and garlic powder.
Roast the potatoes for 40 minutes, flipping once halfway through, until golden brown and crispy.
While the potatoes are roasting, make the ginger scallion sauce: Heat the avocado oil in a small saucepan over medium-high heat until the temperature reaches 375°F (190°C).
Add the scallions, garlic, ginger and salt to a medium heatproof bowl. Carefully pour the hot oil into the bowl. The mixture will sizzle a lot. Once the aromatics stop sizzling, stir with a spoon until evenly mixed. Set aside until ready to use.
To serve, transfer the roasted potatoes to a platter and top with the ginger scallion sauce. Serve immediately.