Butterfly guard is a classic starting position for this technique, although there are other scenarios where you can definitely hit this move. Begin with your right hand deep in your partner's collar (as opposed to classic underhooks or overhooks). Now, step your left leg out from inside your partner's guard, effectively accepting a half guard (oftentimes, butterfly guard is considered a step up from half guard, so people will usually accept this maneuver). The advantage here: You've set the bait for your partner, who now believes they can pass your guard to your left (after all, there's no butterfly hook there anymore). Nevertheless, they absolutely will be able to get to your half guard.

Here's where knowing what your partner is likely to do comes in handy. In order to pass your half guard, they are likely to need to bring their head over to the other side of your body (this applies to the hip-switch method as well). This will give you the opportunity to finish the choke with the second hand (same principles as the cross choke from the mount).