Preheat the oven to 350 degrees.
In a small bowl, whisk together the flour, baking powder, baking soda, and salt. Set aside.
In the bowl of a stand mixer, mix together the eggs, the juice from the pineapple can (about 2/3 cup), 1 1/4 cups maple syrup, 1/2 cup melted coconut oil, and vanilla extract. Add the dry ingredients and mix to combine.
Pour the remaining 1/4 cup melted coconut oil in the bottom of a 9 by 13 inch pan. Arrange 8 pineapple slices in the pan, then drizzle with the remaining 1/4 cup of maple syrup. Spread the batter on top. (Note: You can add a few more half slices of pineapple if desired.)
Transfer the pan to the oven and bake on the center oven rack for about 30 minutes, or until a cake tester inserted in the center comes out clean.
Remove the pan to a wire rack, and loosen the edges with a spatula. After letting the cake cool for a few minutes in the pan, turn the cake onto a serving platter. Carefully remove the pan, and let the cake cool on the platter before cutting.