The tension of the trap holds it on the stick or the piece of white pipe. It's just a tight fit.

This picture is not ideal it is just the only one I have and so it should be noted you want the catch hanging free like in white's picturenot stuck close to the tree like this one because the shrews might get it.

I usually use a coni-bracket, located maybe an inch or so below the pot.

If you aren't using belisles, this is how I would set them up. I let the lip of the flowerpot hold the trap in place, when it goes off it swings free and the marten will hang.

Has anyone perfected a set like this for raccoon?

No coon up here.

If you go into the wilderness archives there is a really great thread on marten traps. You can use a conibracket or a newpaper tube. With the tubes they hold the trap. You can use nails or whatever. Anything that will stabilize the trap. Go through that thread and it will make sense.