The easiest way to learn a Backside 180 is to practice it with the image of adding an Ollie to a backside 180 powerslide. You will not get much height with this method, but as you get used to it, you will naturally understand how to make your Backside 180 higher and more stable. In this section, I will not go into the technique for height and stability, but instead focus on the quick, low 180 as the first step.
STEP BY STEP TUTORIAL
1. Add an Ollie to a Backside 180 powerslide

The motion of a Backside 180 powerslide is almost the same as a Backside 180 Ollie, except without the Ollie itself. The best time to learn this trick is after you are somewhat comfortable with Ollies, but mastering the Backside 180 powerslide beforehand will make learning much easier. In the following, I will explain the details by comparing the two tricks.
2. Start rotating your upper body while bending your knees.

At the beginning, to build rotational momentum, lightly twist your upper body in the opposite direction, then rotate backside. This movement is the same for both tricks, but the difference with the Ollie compared to the powerslide is that you need to bend your knees slightly to pop the tail. Keep your balance even while bending your knees, and focus on making a solid upper body rotation. Do not rush—slow and controlled rotation is what matters.
3. How to Pop tail

In terms of timing, with a Backside 180 powerslide you rotate 180° around your back wheels while turning your upper body, and the key moment is when the nose lifts and the board begins to rotate. At that point, use the tension created in your back foot from your upper body rotation, and pop the tail straight down just like in an Ollie.
4. Push the tail forward in the direction of travel with your back foot.

Once you pop the tail firmly and the board lifts, use your back foot to push the tail forward in the direction of travel to complete the rotation. When you land, keeping your eyes facing directly behind you will help with stability. You do not need to force your board or upper body to turn, but if your weight shifts too far forward while focusing on your back foot, you will get stuck. Keep your weight centered over the board and focus on precise movements. With this approach, you should be able to land the trick in a relatively short time.