Once it is spread on the cake, my BC seems to have tiny craters. I'm guessing they are air bubbles or something. Even when I smooth the cake they don't go away. Why is it not smooth? What am I doing wrong? Some advice, PLEASE...

Start with a great recipe. Sometimes the airbubbles are the problem. Mixing it in high mode right away will also cause airbubbles.

many here LOVE, just absolutely LOVE SugarShack's buttercream:

the recipe:

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also, I cream all the fats and liquids together until light and fluffy.
then add the PS and mix at a low speed (2 on my KA) for a longer time.
seems to be working so far.