I've had a Mineral B for some time now, but I'm not too happy with the development of the surface. When I bought it, I warmed it up a few times with oil in, but at the stove, not in the oven. It has gotten layers of black, but it's erratic and some parts are slightly more raised than others. What can I do to make sure I develop the pan better? Can I season it in the oven now, or should I lightly sand off some of the blackness that is already there and then season it?