To get an enemy airborne you have to pound on the ground, by holding when in the air.
The level to try this in is the third (Days of Future Beginnings), and the section is Betrayal. You will first need to eliminate enemies in a courtyard and then advance into a section with three statues. To move these statues you need to operate a wheel. Go get the part needed to assemble the wheel, as soon as you have it (first you have to defeat a Hunter and Machete Champion) a lot of machete enemies will come out. Hold to block and let six enemies close in around you. Once you have six enemies surrounding you, jump up and do a ground pound to get the enemies airborne. After doing this, unleash a Claw Spin attack on them to get the Slice 'n Dice achievement as well in one go.