Whisk your sourdough starter discard with milk, maple, vanilla extract, then add the gluten free oat flour, and almond flour. Whisk to incorporate.
Cover the mixture and let it rest at room temperature overnight for 8 - 12 hours. The mixture will ferment overnight and be fluffy the next morning (it will look dryish).
The next morning, to the fluffy sourdough mixture whisk in the egg, butter or oil, baking powder and soda, and salt. The mixture will seem dryish at first, but once the ingredients are incorporated, the batter will be thinner. Whisk to incorporate the ingredients. You'll notice right away how fluffy and light the batter becomes.
Heat a nonstick griddle or skillet on medium heat (375-400f / 190-204c). Before scooping the batter, stir it down (you may have to do this several times through the cooking process because the batter is so fluffy!). There's no need to oil or butter the pan if using a nonstick pan. If not using a non stick pan, lightly oil or butter the pan.
Use a measuring cup to scoop up the batter, add about 3 Tbs to the griddle and spread it gently in a circle pattern (the pancakes will be about 4" in diameter). When bubbles start appearing towards the center of the pancake, gently lift the edge of the pancake to see if it's golden-brown. Bake a little longer if needed. Flip the pancake when the color is to your liking or bubbles appear around the edges with a few on top. Cook the pancake until the underside is golden-brown and the pancake is cooked through.