If you read the bolded points, I don't say to cast just one large creatures; I say to cast a large creature followed by 1-2 smaller, medium sized ones. I suppose I should clarify that by medium size I mean around 12-13 mana, which seems to be the point at which creatures start rolling higher than 4 attack dice.
So, if you wanted a good Warlock opening, you could do something like Turn 1 = QC Mana Crystal, move, Mana Crystal, Turn 2 = Ring of Curses, move, Turn 3 = Adramelech, Turn 4 = Bloodreaper Slayer, Turn 5 = Slayer, or maybe a Hellion.
You could opt for a faster start with Turn 1 = Mana Crystal, move, move, Turn 2 = Adramelech, Turn 3 = Bloodreaper Slayer, but the first opening is more forgiving if you aren't used to playing extremely aggressively (which is harder now with the new Intercept creatures).