Step 1: Preheat your oven to 325°F (160°C). Lightly grease an 8x8 inch (20x20 cm) square baking pan, or line with parchment paper, leaving an overhang on two sides for easy removal.
Step 2: Spread the desiccated coconut evenly on a baking sheet. Toast in the preheated oven for 5-7 minutes, stirring occasionally, until golden brown and fragrant. Keep a close eye on it, as coconut can burn quickly. Remove from oven and let cool completely.
Step 3: In a large mixing bowl, using an electric mixer, cream together the room-temperature unsalted butter and granulated sugar on medium speed until light and fluffy, about 3-4 minutes. Scrape down the sides of the bowl as needed.
Step 4: Gradually add the all-purpose flour, salt, and cooled toasted coconut to the creamed butter mixture. Mix on low speed until just combined. The dough will be thick and crumbly but should come together when pressed. Do not overmix.
Step 5: Press the dough evenly into the prepared baking pan. Use the back of a spoon or your fingers to make sure it's compacted and smooth. Prick the entire surface of the dough with a fork.
Step 6: Bake for 28-35 minutes, or until the edges are lightly golden brown. The center might still look a little pale, but it will firm up as it cools. Avoid over-baking.
Step 7: Remove the pan from the oven. While still warm, cut the shortbread into 16 squares or rectangular fingers using a sharp knife. Let the shortbread cool completely in the pan on a wire rack before removing the pieces.