Try to put the pavement slide glove somewhat close to the forward portion of the board where it is comfortable enough to put your weight on this hand. This position varies by rider and you need to experiment with hand placement for yourself. This is usually intuitive. If you put your hand too far away from the edge of the board your balance will be off and the slide will be harder or you may fall.
Also during your heelside carve and slide, don't look at the ground. Keep your head up, your back foot flat on the board, and your front knee pointing up.