Things You'll Need
Instructions
Dig two blocks deep and two blocks wide for about three sections. Be sure to leave one row of blocks behind you that is one block higher at the base of the channel. This is a relatively decent size to make a test trap, but you can try others.
Dig down one block, after creating the base, and make this section eight blocks long. Keep these blocks at the same height. If any elevation changes occur, then just dig a block deeper.
Go down one more block and make this section eight blocks long. After that dig down a block once more and make that last section eight blocks as well.
Add blocks if needed to make sure the wall is too high for anything to jump out at the end. Then use the two blocks right against the end wall to dig down four blocks.
Make a tunnel away from the rest of the channel about 2-by-2-by-3. Dig that tunnel as far as you like.
Dig up one block to act as a platform after this is complete. Then dig towards the surface, building yourself a staircase as you go.
Fill your bucket with water and return to where your channel starts. Place the water on the block that you left higher than the first section. The water should start to flow through the channel, stopping right before it goes over the ledge where the tunnel is. Do this again with another bucket.
Drop down into your tunnel and stick two buckets of water at the base of the ledge where the water should come down.
Create a wall from blocks in the tunnel to keep the monster from escaping. Place them and leave a row of water outside the wall to collect goodies that enemies drop after drowning.
Test the trap with animals by pushing them into the channel.
Test with different enemies by luring them to fall in so you know what the channel can kill.