Interim: stack up 2-3 courses of concrete block leaving an fire door opening in one end. Place a cooking grate (rebar & any old grill grate), add 2-3 more courses of block. Get a chunk of tin or sheet metal for a roof & another for a door cover. Light a fire, add the meat, close her up with a final block holding the tin down and another for the door adjust the top & door for draft. I cooked butt, chicken & ribs like this for 15 years.
PS: Get LOTS of beer - you will be fire tending a lot more than with the WSM or UDS.
Weber 26.75 OTG w/CI grates & SJ/WSM Mini
Home built 24"x72" reverse flow stick burner trailer with 18"x44" grill w/CI grates and upright SS gas oven/smoker.
Home built 48" fire pit with a 30"x30" Santa Maria style ranch grill.
Home built lump charcoal retort, iGrill & a bunch of other cooking toys.