Step 1: Use Your Strong Foot First, But Don't Forget the Other
It's just like juggling a ball; most people starts off practicing with one foot; and they end up just using one foot for juggling; but for me, I started practicing for both foot so you can develop both foot smoother. And you can use your second foot as a trump card.. (saves, last second resort; etc.)
Always practice both sides~
Step 2: The Tap or Slide
Tap: Tapping for Elastico's is probably the easiest one to learn first. You tap the ball using your outer toe area (outside the pinky foot) And catch up with the ball by dragging your legs (using your knees and thighs) forward in a diagonal angle. So it ends up around 2 Taps total (1 tap for outside diagonal and 2nd tap for the opposite bounce), and once you stomp, rotate your foot around 20 degrees angle pointing the opposite bounce side.
Tapping is easier to learn; But harder to pull off once your dynamic (moving). Or sprinting.
Slide: On the other hand, Sliding is harder to learn; but easier to pull off once your sprinting or moving quick. For the slide, you have to "Drag" the ball outwards diagonally (similar to tap). (like pushing a ball with your legs instead of kicking it), then bring it back by stomping and changing angles of your foot.
Step 3: Extra Tips or Notes
If your having a hard time with this trick; Or you manage to do this but doesn't look deceiving:
Try arching your foot downwards.
If the ball flies off during the first tap or slide:
Try practicing the trick in a slower pace. And build up the speed once your confident.
If you want to practice this trick quicker, while confident with your skills:
Try dragging the ball back using your weak foot; then attempt it over and over again. This is the key on getting better with this trick. (shown in the video on "intro section")
If you have any questions; feel free to post it.
Sorry for my grammar; English is not my native language. ^^.