We just had a big halloween party and my dad does this every year. Delicious! Probably works well with any kind of red meat but we use venison.

Marinade a roast (approx. 7-10 lbs) in italian dressing for a few days.
Build a big hot campfire and let it burn for about 3 hours until it is nothing but really really hot coals. Take the roast and wrap it entirely in uncooked bacon. Attach bacon by pinning it on with toothpicks. Then take an empty Pepsi 24 pack Cube cardboard box and fill it half way with salt. Place the roast in the middle and fill to the top with salt covering the roast. Wet box to keep it from burning up to quickly. Also helps to wrap box in duck tape. Carefully place the box in the center of the hot coals and quickly but gently build wood all the way around and overtop, carefully so it doesnt fall apart. By the time the box burns away, the salt crystalizes into a weak salt block, cooking the roast inside. Let this cook a little over 3 hours before removing and keep the fire fed so it remains really hot and intense. Always set the wood on gently however because the salt block is weak and will break. If it breaks a little dont discourage just cut off the charrred meat after you pull it out. The best way to pull it out is with a flat shovel so no one gets burnt! Lots of fun at a hunting camp.