Is it permissible for a woman to teach women's handicrafts on YouTube, with only the hand and palm visible, and wearing a wristband to prevent any other part of the arm from showing? And does the fact that the work is not of interest to men change the ruling?

In summary: The ruling on looking at the severed hands of a woman is based on the ruling regarding a woman's baring of her hands, which is a matter of scholarly disagreement. The way out of this disagreement is for the sister who asked the question to wear gloves. The ruling does not change if the face is not visible, for whoever prohibits looking at any part of a woman's body also prohibits looking at it separately, even if it has been detached from her body.