I am highly intrigued. I never once have considered the possibilities of ceramic bread-baking utensils. Certainly not unglazed food-carrying things. How interesting.
On a technical level, I suppose a groggy clay would be best suited to something like this; the grog would help to avoid cracks over time. Either earthenware or stoneware… the studio reclaim would actually be sort of ideal. Maybe even the beachfire clay. Hm.