Put on the Scavenger perk and use claymores. You can put one down and when it kills someone you can scavenge his body for another. You can also scavenge when you already have one down, get another, and place it somewhere else. You can only carry one at a time but you can put down as many as desired. It works best to hold up in a room. Every time someone comes through it goes claymore, scavenge, set, and repeat.