I think a pulley would be able to use because maybe he could step in the rope and it will pull him up.
First, you have to lift the inclined plane. Then attache the bait to the wedge. After you put the bait on, you have to stick the wedge in between the inclined plane. If the leprechaun tugs on the bait the wedge will get knocked over and the inclined plane will fall.
I ended up not using the pulley, but the wedge ended up being good anyway.
The trap that I made turned out great. The leprechaun really fell for it.