Can I play Stacked Deck without having at least 3 cards in my deck?

Yes, you can. Stacked Deck instructs you to look at the top 3 cards — if you have fewer than 3 cards remaining, you simply look at as many as are there and resolve the effect normally (put 1 into your hand, recycle the rest). You do not need at least 3 cards to play it.

The only time you can't play Stacked Deck is if your Main Deck is empty (0 cards), because there's nothing to look at. (FAQ #2237)