Start in a good front mount position.

With your non-dominant hand, open his same-side lapel.

Slide the thumb of your dominant hand deep into his opposite-side lapel, which you are holding open.

Close your hand into a fist - with his lapel inside - and place that fist onto the mats.

Reach the fingers of your non-dominant hand underneath your other arm and into his opposite-side lapel. You shouldn’t be too close to his neck, else your non-dominant hand will be in the way of the choke. Use the picture as a reference.

Bend your torso forward while bringing your dominant-side forearm down across his neck, like an old-school paper-cutter. If he tries to block by keeping his chin tightly down, you can use your forearm to dig underneath and push his head upward. Try to apply enough pressure to turn his face to the side, and keep bringing your elbow down toward the mats until you get the tap.