Place potatoes in a large pot, add 1 tbsp salt and water until the potatoes are submerged and covered by 2.5 cm of additional water. Bring to a boil over medium-high heat and cook for 20 minutes or until potatoes are fork tender, then drain them.
Mix ingredients for dipping sauce in a small bowl and set aside.
Brush a large baking sheet with 1 tbsp avocado oil then place the potatoes on the sheet. Place another baking sheet on top and press to smash all potatoes evenly. Drizzle potatoes with remaining avocado oil and add flaky sea salt and pepper to taste. Bake for 30 minutes or until crispy and golden brown.
Remove from oven and top with sesame oil, sesame seeds and gochugaru flakes. Serve with the dipping sauce.