Karas's Box is a difficult
variation of the Box presumably established by
Michael Karas in which the
horizontal pass is made to the same hand that threw it, and then passed back
across the body in a similar manner. This contrasts with the Bizarre Box
(which is a necessary prerequisite for Karas's Box), where you make only one
"pass", and then carry the ball back to the other side of your body. This
trick is one of the most difficult Box variations, since the "passes"
require accuracy and careful timing to work effectively.
To learn Karas's Box, start with one ball in your non-dominant hand. Cross your non-dominant hand underneath your dominant hand, and then make a very low throw from your non-dominant hand toward the non-dominant side of your body. Right after you make this throw, uncross your hands, catching the thrown ball in your non-dominant hand.
Practice this on both sides. To add in the second ball, start with one ball in each hand. Cross your non-dominant hand underneath your dominant hand, and then simultaneously make a vertical throw from your dominant hand and a "pass" from your non-dominant hand like the one made in the previous step. Catch the "pass" in your non-dominant hand, and then make an actual horizontal pass to your dominant hand, clearing space for your non-dominant hand to catch the vertical ball.
Practice this throw combination on both sides. It will likely feel very awkward at first, since your hands will naturally want to make throws of roughly equal height. However, with practice the throws should become second nature. Before you can add in the third ball, there is one more two ball exercise to learn. Start with two balls in your non-dominant hand, and then cross your non-dominant hand underneath your dominant hand. Make a vertical throw from your non-dominant hand and then, as that ball begins to descend, make the "pass" that you did in step one, uncrossing your hands and catching the vertical ball with your dominant hand.
Once again, practice this throw combination on both sides. To finally add in the third ball, start with two balls in your non-dominant hand and one ball in your dominant. Cross your non-dominant hand underneath your dominant hand, and then make a vertical throw from your non-dominant hand. As that ball reaches its peak and begins to descend, make a vertical throw from your dominant hand while simultaneously making a "pass" from your non-dominant hand to itself. Your hands should now be uncrossed at this point, with your dominant hand catching the first vertical ball. The second vertical ball should now be descending toward your non-dominant hand, which will make a horizontal pass to your dominant hand to clear space for a catch.
As shown, practice this on both sides. To create a full cycle of Karas's Box, you are going to insert the previous step into a cycle of the Bizarre Box. Start by juggling the regular Box, and then transition into the Bizarre Box by making a "pass" from an uncrossed position into a crossed-arm position. In the Bizarre Box, you would then carry the passed ball back around as you uncrossed your arms. In Karas's Box, you are going to make another "pass" back across your body, while also doing a vertical throw from your other hand. You will then resume juggling the regular Box.
Practice doing one complete cycle on each side. To run the full Karas's Box, simply a single normal vertical throw/horizontal pass combination (like you would do in the regular Box) after each cycle. This will set you up to do another cycle using the opposite hand configuration. Karas's Box is not an easy pattern, so expect to spend a lot of time mastering the trick.