Preheat oven to 350 degrees.
Grease a donut baking pan with coconut oil.
Combine in a large mixing bowl: flour, salt, baking powder, sugar.In a small bowl, combine the flax seed, water, non-dairy milk, vinegar and vanilla. Whisk briskly for a minute, then set aside to allow the flax seed to thicken the liquid. Whisk one more time before adding to the dry mixing bowl.Also add the coconut oil to the mixing bowl. Stir briskly until fluffy and well-combined. The batter will be fluffy and like a very wet bread dough.
Spoon the batter into the donut tin. If you fill the donut pan to the brim, you will get nice and fluffy donuts. If you only half fill, you will get half-formed donuts. Your choice. I like to fill mine to the brim.
Bake at 350 degrees for 12 minutes.
Cool donuts for a few minutes before carefully loosening with a butter knife and transferring to a cooling rack.
Whisk together you glaze. You can add coloring or not. You also have the option of making chocolate glaze instead. Chocolate glaze reduces the sugar to ¾ cup and then adds in 2 ½ tablespoon cocoa powder. I usually increase the oil to a full tablespoon for my chocolate glaze.
When the donuts are cooled, you can dip them in the glaze. Let them drip and 'dry' on the cooling rack, then dip again. I usually do at least three dips for maximum glazed coating.
Add any additional toppings you'd like. Serve. Store leftovers, covered, in the fridge for up to a few days.