There is alot of confusion and misinformation regarding making these by hand. You must have the "Heating: Beginner: knowledge to do so, if you do not it will tell you that it is not working at all when you try to heat melted ore. You get this knowledge from the Quest "Pure Water for an Experiment" in Heidal. Here is about the best information I found on it. The Quest NPC will offer you a quest to learn from three people, the heating person then gives you this quest.

http://forum.blackdesertonline.com/index.php?/topic/27382-iron-ingot-making-them-by-hand/