Their grill is used for ground fires only. The way they do it is interesting. A layer of sod is lifted from some other location and layed down on the ground upside down. On the exposed soil is where the fire is then made.
I prefer a fire box. While any type of above ground fire is not really medieval, the box makes for a cleaner fire site than using sod.
The lid of the box has several neat functions:
The whole assembly is big enough to hold two full sized cooking pots
Medieval grill as Freehand document (.fh9)