There are places where one can go and buy a piece of pottery (that is usually ceramic etc.) and paint it yourself according to how you want it to look. Generally, one chooses a cup etc. paints it with paints that the studio provides, pays for it, leaves it in the shop for them to place the piece in the kiln or oven to give it a shiny and finished look. Afterwards one comes to pick it up. Would this require tevilla (without a brocha) like any other earthenware or is that called nigmar b’yad yisroel?
Nigmar b’yad Yisroel is not the point here, rather if it is made of materials that require tevila. We only have to tovel metal and glass, china has a glass coating on it, there fore we tovel it without a bracha. Cheap pottery, that doesn’t have a glass coating does not need teliva at all.