1. Take Apple 7 as an example. You can use the third-party software "clip" to make a slow-motion video. First, you have to open the "Clipping" on your mobile phone.

2. After opening, click the "Start Creating" button in the interface.

3. Select the video to be made in slow motion in the camera.

4. Then click the "Clip" button at the bottom of the interface.

5. Then select "Variable Speed" in the pop-up options.

6. You can use video to speed up or slow down by moving the red button on the speed change bar. To slow it down, you need to move it up to the left, which can slow the video by 10 times at most.