I did almost the exact setup awhile back. Used loose cinderblocks and put a piece of welded wire grating and then stacked up more cinderblocks on top. The result was a three sided grill with no top or front. I then put a piece of ply on top with a hinged front. The fire didn't get so hot as to burn the plywood. It kept in the heat and smoke well enough. Control heat by amount of wood/coals in the contraption.
