How should I position the minions when playing against a Mill Rogue’s Vanish

Cards to consider adding vs aggro decks:

• 1 Blizzard - I would highly recommend you put these in, due to the fact that they both freeze all your opponent's minions, AND do 2 damage to all of them, killing a large number of aggro creatures and stalling others.

• 2 Vaporize - If you're keeping the board clear of smaller minions, this'll help you take care of bigger minions if used properly.

• 1 Arcane Missiles - Can 2 for 1 against aggro rush decks, assist in taking down 2 toughness or greater minions. Cons - Based on RNG.

• 2 Mirror Image AND/OR 2 Ice Barrier AND/OR 2 Frost Nova - One of the biggest counters to an aggro deck is stalling it out, especially in a Mage deck where you can pull a turn 7 flamestrike. These 3 cards are all excellent for stalling, as Mirror Image basically prevents 2 creatures from doing damage, even charge creatures, Ice Barrier, being a secret, can cause your opponent to play abnormally, such as playing a smaller minion than they would have because they're afraid of Mirror Entity. In addition, it basically heals you 8, even if you're at full health, which is pretty solid vs an aggro deck. Frost Nova is likely the weakest at stalling an aggro deck, due to not effecting charge minions at all, but is more relevant typically late game, due to effecting all of your opponents minions out currently.

• 2 Cone of Cold - While Arcane Explosion is generally considered a bad card, Cone of Cold is relevant at times, due to the fact that those minions it doesn't kill with it's 1 damage will still be frozen for a turn, making it still a relevant card in the late game.

Cards to change out:

• 1 Gadgetzan Auctioneer -> 1 Acolyte of Pain - Gadgetzan Auctioneer isn't necessarily guaranteed to draw you a card when you play it, and is a high costing 5 drop, with not very high toughness. Alternatively, Acolyte of Pain is almost always guaranteed to draw you a card, unless silenced or straight up destroyed, and, when combined with your hero power, will be able to trade for 2 toughness or less creatures well.

• 1 Argent Squire -> 1 Mana Wyrm - Mana Wyrm is one of the best 1 drop minions in the game, very often 2 for 1's, or at the very least, trades up. Argent Squire CAN 2 for 1, but only against 1 toughness creatures. In addition, it doesn't have ANY impact late game, whereas a mana wyrm can.

Cards to consider taking out:

• 1 Sunfury Protector - While not the worst card, this is the kind of card that doesn't really do anything unless you have other cards to go with it. In this case, those other cards happen to be minions. When combined with a Chillwind Yeti, or better yet, a boulderfist ogre, it can be very powerful, but without one of those, it doesn't necessarily do much. If you still like the synergy of it with minions such as these, I would recommend replacing it with Defender of Argus, as you're almost never going to be playing Sunfury Protector before turn 5 or so anyways, and Defender of Argus is more relevant with minions such as Acolyte of Pain and Mana Wyrm

• 1 Azure Drake AND/OR 2 Boulderfist Ogres - If Aggro decks are really your only weakness, I would consider removing some of these more expensive creatures. Boulderfist Ogre is particularly useless against aggro decks, because they will just proceed to ignore your ogre, since they likely have you far lower at the point you play it than you do them, and you can only use it to kill one minion of theirs a turn.

As a counterpoint to my other answer, here are the main ways that a zoolock deck can use against board clears:

• Control/Apply pressure early. If you can make them feel pressured with 2-3 early creatures it may draw out their board clear earlier than they'd like. You might want to consider dropping your shield bearers for a little more early game pressure such as elven archer for the 1 damage(take out a potential totem they might have) or stonetusk for the charge. Leper gnomes are also great for dealing a bit of damage.

• Throw in more divine shields. Divine shielded minions force the other side to use multiple board clears. Argent protector and Scarlet Crusaders will force them to come up with a way to remove the shield first.

• Filling the board via 2 for 1 cards, such as Murloc Tidehunter or Razorfen Hunter may bait the card out earlier as well as save you a card if they do clear the board.

• Use bigger creatures. Succubus is a cheap 4/3, which gives them a chance to survive lightning 50% of the time (its a great lightning bolt bait though). If you boost them with a +1/+1 from a cleric next turn then it becomes much harder to remove.