You get into swim-mine/crawl mode into a one by one hole, when someone follows you you mine the block above their head (so it forces them into standing mode), then place a pressure plate at their feet, a sign on the pressure plate, and a water bucket also on the bucket plate. The pressure plate prevents them from crawling, the sign prevents them from hitting/mining, and the water makes it take longer to mine. Pro tip: Hit their feet and win!