Preheat oven to 325 degrees F (165 degrees C). Spray 36 mini muffin cups with cooking spray or line with paper liners.
Whisk flour, baking soda, cinnamon, baking powder, salt, ginger, cloves, and allspice together in a bowl. Beat white sugar, brown sugar, eggs, and vanilla extract together in a separate bowl using an electric mixer until well blended; beat in pumpkin and coconut oil until just combined.
Stir flour mixture into pumpkin mixture until batter is well mixed. Pour batter into the prepared muffin cups, filling 1/4-inch from the top; sprinkle with almond slices.
Bake in the preheated oven until a toothpick inserted in the middle of a muffin comes out clean, about 11 minutes. Cool muffins in the pans for 2 minutes before transferring to a wire rack. Cool muffins for 5 minutes on rack; sift confectioners' sugar over muffins.