I ordered the plank mechanism on Ebay from a guy in KY that makes them, $15 if I remember correctly. There are some cheaper Chinese knockoffs on Ebay, but they didn't have very good feedback ratings.
The instructions with the one I got recommended cutting a rectangular hole in the side of a five gallon bucket just under the lid lip and have the ramp go up to the hole. You can just route the ramp to go over the top of the bucket, but I like the hole idea better. That's how I did it.
Since the trap is at a remote property I own, I am not able to check it daily or even weekly, just when I go to the property. I substituted antifreeze for water in the bucket. I don't notice any smell when I check it. I use peanut butter as the enticement for the mice to "walk the plank" to their demise. I got 19 the first setting. The numbers are now decreasing, but I feel comfortable that is due to a greatly reduced population.