A method of operating a channel induction furnace to process a feed material and obtain therefrom at least one of a molten metal product, a vapor phase metal product and a slag product. The method involves maintaining a slag layer on the molten bath that has a thickness that is sufficient to support the feed material while minimizing heat transfer through the slag layer and minimizing the resistance of vapor phase components from transferring through the slag layer. The fluidity of the slag layer is controlled by heating the slag layer and adjusting the chemistry of the slag layer.