[@Chasebloodcrest]
Or write in a notebook with 1001 ways to kill the character, how to chop and cut them up, and ways to dispose the body. Leave the notebook out by accident one day and when questioned by someone in your house you can simply reply with "Oh, just ideas..." 

Then you can watch that person slowly start to panic as they constantly go back and read that little death book. 

You can also do things like leave it near the sink with the biggest knife just lying in the actual bowl; or receipts for hand saws, bolt cutters, and rope (but you don't show them the return receipt for those products, you just want that purchase receipt).

Life is fun when those around you are going insane. :sun