In a microwave-safe mug (at least 12 ounces), whisk together the flour, sugar, baking powder, and salt with a fork until no lumps remain.
Add the milk, oil, vanilla extract, and almond extract to the dry ingredients. Stir vigorously for 20-30 seconds until the batter is completely smooth with no flour pockets visible.
Sprinkle the sliced almonds evenly over the top of the batter, gently pressing them down slightly so they adhere.
Microwave on high power for 60 seconds, then check for doneness. The top should look just set with a few moist spots. If needed, continue cooking in 10-second intervals until a toothpick inserted in the center comes out with just a few moist crumbs.
Let the mug cake rest for 30 seconds to finish cooking from residual steam and to cool slightly before eating.
Enjoy directly from the mug with a spoon, or carefully turn out onto a plate if desired. Top with whipped cream, ice cream, or fresh fruit if you like.