This is the easiest part to build. Just take the hard wood as a base, and fix the strips of wood in each side of the hard wood. Then take the smaller strip of wood and fix it on the base making a diagonal. This will give sustentation in the null button when you step on it (or jump/stomp). It works pretty well, I made a party in my house and everyone danced in my pad all night long, and it's still intact.
        Next, fix the top wood in the laterals and your null button is done. Be sure to use the thicker wood as the top since it's more resistent. Below are a couple of pictures of the null button: