Obviously, what you see here is an un-adorned form. I'd stick with this until you get the whistle part down. Once you get it to whistle you can pierce the chamber to get multiple tones. The additional tone holes can be placed anywhere you want to put your finger. As I mentioned somewhere earlier, the size of the chamber impacts the initial tone.
Small chambers tend to produce very high tones.
They usually require a good blow to get the sound. A larger chamber produces lower tones and often will only sound with soft, gentle breaths. If it doesn't whistle now, it will not , and I really mean this, it will not miraculously start whistling after it is fired. If you are prissy about putting wet clay in your mouth then find a geezer to test it for you. Remember, this is a wind instrument.