I'm thinking something along the lines of the pit that inspired the artist that drew this political cartoon from around 1830. I think it should be pretty easy to have access in the center for spreading coals and an opening on the end for a fire to cook Texas style.
I want it to have a brick veneer but I'm not sure how to build the floor or the sides. I figure a metal lid and doors could be made for the side and end fire access so they can be closed while cooking or when not being used.