Save penalties as the keeper. Stay big and balanced, read the taker, delay the dive so you do not commit early, and spring low and strong to keep it out.
Takers strike penalties and the keeper works on saving them. Stay big on the line, read the run-up and body shape, delay the dive, then spring low and strong to the corner. Vary the placement. Emphasise not committing early and a powerful, low dive. Rotate takers to vary the picture.
Roughly three penalties in four are scored, which means a keeper walks to his line with nothing to lose and everything to gain. That framing matters, because a keeper who feels he ought to save it guesses early, and guessing early is the one thing that converts a difficult save into an impossible one.
Delay is the whole technique. Every fraction of a second a keeper stays balanced and central is a fraction in which the taker might reveal something, and revealing something is what most takers do. Diving before contact turns the penalty into a coin flip in which the taker holds the coin. Staying up until the strike means a lower chance of reaching the corner but a real chance on anything struck at a saveable height.
The reliable cue is the plant foot, not the eyes and not the shoulders, both of which good takers use to deceive. The standing foot has to point somewhere close to where the ball is going, and it lands a fraction before contact. A keeper trained to watch that one thing has a genuine read rather than a guess.
The spring itself should be low and long rather than high and pretty. Most penalties are struck below waist height, so a keeper who launches upwards travels over the ball he was trying to reach.
Saving a penalty is a bonus, not a duty, and coaching it that way produces keepers who stay big rather than keepers who dive early to look committed.
Save it to your private drills, then change the animation, adjust positions, swap equipment, or drop it into a session block. Or start from a blank pitch and build your own.