Flo's Mess is a variation of
the standard Mills Mess in which one of the balls is carried from the middle
of the pattern to the outside, creating a Windmill-like effect that
alternates sides. Visually, Flo's Mess appears only subtly different from
Mills Mess, so spectators may not be that impressed when you switch between
To learn Flo's Mess, start by juggling a regular Mills Mess pattern. Then, during one of the cycles, you are going to make an overthrow from the hand holding the third ball (the one thrown last during a cycle) and grab the middle ball. From you other hand, throw the ball that used to be first in the cycle (it will now be second) under the arm of the hand that caught the middle such that it follow the same path as the first overthrow. Finally, make another overthrow with the middle ball you caught earlier.
Practice this on both sides. The full Flo's Mess consists of repeating cycles of these three throws made on alternating sides, so in the final step you will chain two of these cycles together. Start by juggling a regular Mills Mess, then transition into the three throws made in step one. After making the last throw, your are going to repeat each of the three throws on the other side of your body, using the same ball that was used in the previous cycle. The first throw will be an overthrow, followed by an under the arm throw, followed by another overthrow.
To run the full Flo's Mess, just keep repeating the cycle on each side (the final throw in the animation above shows the beginning of a third cycle). When done correctly, the trick should feel like a Windmill that alternates sides after a couple of throws.