Stand low with feet about 70cm apart. Lower your body, until your thighs are parallel to the ground, keep torso straight. In this entire juggling routine, you are to be in that fixed stance. Now, do a cascade. When it is time for the right hand to catch, move the right hand under the right leg (from the outer side) and throw the ball towards your, face and catch the falling ball. Then, immediately do the same with the left hand. Once the left hand is done, do a regular cycle of cascade (with hands not under the legs). Then, go back to hands under the legs.
In summary, stand with legs apart and fixed to the ground, and juggle with both hands under both legs, for every odd cycle.
Do this with fluidity and elegance, not with a “Look ma i can do this!” attitude.
A important aspect of this trick is your flexibility and stamina with your legs. Better do plenty of warm up on your knees. Like a kung-fu stance, you'll get better and better with this as a Anaerobic exercise. (be careful here… you should not be too old, or should be very atheletic, to practice this trick. Else it may damage your knees. And if you are young, remember to always warm up, because this can cause knee damage when you get old)
The following is similar to the above, but easier.
Stand with legs lightly apart. Twist your upper torso to the left about 60°. Do a cascade. When it is time for the right hand to catch, drop your whole body down as if your legs went limp, and go into a low stance position with your thighs almost level with the ground, then throw the ball high with right hand from under the left leg, and catch the falling ball while right hand is still under the left thigh. Then stand up quick, and resume the previous standing position, with the left hand to do JUST ONE throw and catch, then repeat.
So, when perfected, your body moves up and down, and your right hand is under the left leg for each right hand catch/throw.
When you become familiar with this trick, you can also do the right side version. Then, a nice way to transit from left to right is a throw behind the head move. So, you are like: left squat, one throw to the right, right squat, one throw to the left, left squat …
Again, practice this and envision the final act with elegance and grace, as if you are a figure skater performance in Olympics. If smooth movements is not your style, then try imagine you are in a international dance competition, where your style can be masculine and powerful. The one thing you want, is that you want to have precise control of every part of your body, from the posture of your fingers to your facial expressions. What you do not want to do, is to assume the common juggling attitude: “Hey look! I am able to do this seemingly incredible feat!”
(imagine a figure skater going into Olympics. He jumps into the ice ring, with no music but a idiotic grin. Wearing a t-shirt, ungainly looking like a buffoon. He then do a standard skating trick like backward skating, then stop and stand. Then, for his next trick, with deep breath and drumbeat rising, he does a double axles. And when his arm-flaring succeeded in breaking his fall, he stands with pride and a snickering sense of accomplishment. On occasion, he shakes his head silly so that the audience can be amused. In between tricks, he stands and anticipates the audience to applause or make some approving noise, and will fret and incite his gawkers to do so if they didn't automatically. This, is the state of affairs of juggling acts today.)