Preheat your oven to 325 degrees Fahrenheit (165 degrees Celsius) and grease a 9x13-inch pan with non-stick spray or butter. Then, sprinkle a light coating of flour over the pan to prevent the cake from sticking.
In a large mixing bowl, combine the flour, cinnamon, baking powder, baking soda, and salt. Stir until well combined and set aside.
In a separate bowl, mix the sugar, oil, and eggs together until smooth. Slowly add the dry ingredients to the wet mixture and beat until fully incorporated.
Stir in the grated carrots, crushed pineapple, shredded coconut, and chopped walnuts into the cake batter. Pour the batter into the prepared pan and smooth the top with a spatula.
Bake the cake in the preheated oven for 35-40 minutes, or until a toothpick inserted into the center comes out clean. Once done, remove the cake from the oven and let it cool in the pan for 10 minutes before removing it from the pan and allowing it to cool completely on a wire rack.
