Heat your oven to 200C fan.
Place the potatoes in a large pot and cover with tap water. Add the sodium bicarbonate and bring to a simmer. Simmer for about 15 minutes until a small, sharp knife can be inserted and withdrawn easily.
Drain the potatoes and allow to stand for about 5 minutes to steam dry.
Place a sheet of baking paper into a roasting tray and add about ¼ cup of oil (olive oil, ghee, duck fat or vegetable oil) onto the baking paper.
Place some of the potatoes on top and with a cooking weight or the bottom of a small saucepan, squash the potatoes to about 2cm thick.
Season with a little salt and drizzle with a little more oil.
Roast in the oven for about 40 minutes until the potatoes are browned and crisp.
To serve, season with extra salt and trim away the excess baking paper. Serve and enjoy!