Kioshi Dave Joslin talked about sliding the down foot toward uki when doing a kick. After sending a few standard kicks, with the post foot fixed to the ground, mix in a sliding kick. This disrupts uki's maia.
You don't want to skip or hop forward. Just unweight the down foot so that your forward momentum causes the foot to slip a few inches forward. Keep the post foot on the ground, NO weight on the heal, knees bent with the ball of the foot taking the weight and pivoting so the the heal comes forward of the ball during the slide.
Just adding four or six inches to your kicking range will kuzushi uki. You must train this technique so that it become effortless and natural. If they see it coming they will see it coming.
