We take the same recipe but in the other direction... In backside, the movement can seem slightly less natural but by putting your hand on the ground (always having put on your gloves beforehand slide), you will be able to easily make the wheels of your longboard stall by grabbing your board near the front truck.
Unlike slide in frontside, you can position your back foot at the level of the rail of your longboard and push on it in order to facilitate even more the skidding of the wheels. Be careful not to lean too much towards the road or you will be unbalanced and fall off your board. Try to keep a straight position by concentrating a good part of your weight on your front foot.
To start again, once you have slowed down enough, you just have to stand up and bring your back foot closer to its initial position.