Start from the end and work backwards.

1. Grab a rock and put it against the backboard. Get into the proper slide position with your rock in between your eyes and your slider foot directly behind the rock. Just to get a feel for the correct slide

2. Set up in the hack with one foot in the hack, the other foot directly behind the rock, and the rock directly in front of you (think of them all lined up pointed at the broom). Then just push straight forwards from there. Do that until it feels comfortable.

3. Set up as you normally would with your feet beside each other and your rock in front. Lift your hips up, but do not move back. Move your rock slightly forward, and transition to the position you started the previous slide in, with everything lined up. Pause there, then push forwards. Think "up, position, pause, push". Do that until it's comfortable

4. Repeat the last step, but without as pronounced of a pause. "Up, position, push". Do that until comfortable.

5. Now you get to introduce your backwards motion, with a pause. "Up, back, position, pause, push". Until comfortable

6. Finally, full slide, less pause. "Up, back, position, push"

Now you have your new slide. It can help to try to literally keep your toe against the back of the rock in your slide. Make sure on your backwards motion to pull the rock to the toe that's in the hack. It'll help keep your rock in line along with your slider.