Straighten the trail arm and snap the fingers to square
For the release, the coach wants to feel the trail arm go from bent to straight out of the loaded 'serving the platter' position, with the fingers snapping relative to the palm so the toe squares back up to the heel and the clubface returns to square, releasing the energy down the target line. He contrasts this with the fault of coming into the ball and just holding it, the arm staying bent and the palm accelerating too much, instead of letting the arm straighten and the fingers snap. He pictures the correct move as flicking the ball off the paddle down the target line.
Channel: stayhandsy
Watch official source at 5:22Why this context matters
'Flick the ball off the paddle' and toe-to-heel refer to the paddle-and-ball training aid used throughout the lesson.