Mix flour, sugar, baking powder, baking soda, and salt in a large bowl.

Add butter.

Combine dry ingredients using a pastry blender (or two forks) until butter is reduced to the size of grains of rice.

Add almonds to flour mixture, tossing gently.

Combine eggnog and vinegar in a 2-cup measuring cup, and allow to sit for 2 minutes.

Add egg yolk and vanilla to eggnog mixture, and whisk to combine.

Gradually add liquids to dry ingredients; mix until dough forms a ball. (You may not need to use all of the liquids.)

Place dough on a lightly floured surface and press into an 8-inch round.

Cut into 8 wedges.

Transfer wedges to rimmed cookie sheet, preferably lined with parchment paper.

Bake for 15-20 minutes or until the scones are crusty on top and a tester inserted into the center comes out clean.

Cool for 5 minutes.

Combine powdered sugar and nutmeg in a small bowl, and add eggnog 1 tablespoon at a time.

Stir until you get a thick yet spreadable consistency.

Top each scone with a heaping tablespoon of glaze.

Sprinkle with 1/4 cup sliced almonds. (Do this before the glaze sets.)