This is the audio exerpt of sː spoken within a word. It may sound a little short or unclear, but that's exactly how it's in the real context. For more details, read the below explanation of pronunciation and listen example words that contain sː by pressing the word buttons.
1. Break the airflow by touching your alveolar ridge with the tip of your tongue.
2. Push the air through the interruption to produce an audible friction of the air.
3. Relax your vocal cords.
4. Pronounce this sound noticeably longer than normal ones.