In a large mixing bowl, use a whisk to vigorously mix 1/2 cup of milk with the flax seeds and apple cider vinegar for about a minute. It should be thick and viscous. Add the remaining milk, pumpkin puree, olive oil and maple syrup and whisk until smooth.
Sift in the flour, pumpkin pie spice, baking powder, baking soda and salt. Whisk until relatively smooth, some lumps are okay, be careful not to overmix.
Let the batter rest for about 5 minutes. Preheat a large non-stick skillet over medium heat. Lightly spray the pan with cooking oil. Scoop scant 1/2 cups of batter into the pan, and then, you know, make pancakes.