The best size skillet for making cornbread is a 12 inch cast iron skillet. This size ensures that all your ingredients will mix together evenly. If you use too large of a skillet, the pan will be crowded and your ingredients won't mix together as well. This will result in a cornbread with clumps of dry flour and under-cooked batter. If you use too small a skillet, then the edges of the cornbread will be overcooked and dry, while the center of the cornbread remains undercooked.