Gather pieces, pwn your enemies!
There are 2 options:
2) Alternatively, if you can mulligan for/keep draw cards and focus on getting the combo asap. Best is to spend your draw first then use Stitched Tracker to grab the remaining pieces. Only use Tracking when there is 1 combo piece left, or when you have no choice.
The follow-up also consists of two substeps:
(i) Play Fencing Coach on a turn before you play your OTK. It's possible to play him on the same turn as Emperor Thaurissan, but remember not to use your hero power (HP) if you play him long before your OTK turn. Followed by
(ii) the combo itself is: Clockwork Automaton -> Carnivorous Cube -> 2x Play Dead -> 2 x Feign Death -> HP. This gives you 6 clockworks and a 2^7 (128) dmg hero power. Having only 1Feign Death is usually enough though.
2 x Feign Death can be replaced by 1 x Terrorscale Stalker +Flare for spell hunters, secret paladins and mages. Since you can only play 1 Terrorscale Stalker with a Emperor Thaurissan discount I put only 1. The advantage is that you can pull him via Stitched Tracker.
Using Terrorscale Stalker gives you one less Automaton and *only* 64 HP dmg, but it means you do not have to craft the more expensive Feign Deaths. In most cases double Play Dead, or 4 Automatons is sufficient (32 HP dmg) though.
Zul'jin is not necessary, but his hero power also works with this build. You can also play the Automaton to snipe minions with your hero power in case of emergency. He can be replaced by another Hunter's Mark or Deadly Shot.