Stand with feet a little wider than your hips and hinge forward slightly, letting the kettlebell trace a figure-8 path around and between your legs. Pass it from hand to hand behind each leg rather than in front, so your core has to resist the twist as the weight changes direction. Keep your knees soft and your spine long throughout — this is a hip-hinge position held steady while your arms and shoulders do the passing, not a squat that bobs up and down. The tighter and smoother the figure-8, the more the bracing falls on your obliques and deep core rather than your grip.