That's kind of hard to describe! I removed the stock interior piece from the SA reactor. Then I cut down the thread rod to about an inch and screwed it in the stock threaded hole in the bottom of the reactor, and inserted one of the foam pieces. So now we have an empty reactor with a 1" long rod sticking up in the bottom and foam surrounding it.
Then a bought a piece of thin wall PVC that just fits inside the reactor. I don't recall what size, but if you bring the reactor into HD with you, you will find it (its a standard size). Then I cut it down to 9" I believe, sanded both sides flat, and glued one of the stock bubble plates to one end. On the other end, I glued a 5" or so long rod into the open end, sticking out (the point was so my hand doesn't have to touch the water to pump the reactor). then I simply slid the PVC tube into the reactor and filled it with the appropriate amount of stones. To pump, I just grab the rod, and shake up and down for about 15 seconds.
I am changing my zeo rocks this weekend, so I will get a photo then!
edit: here's a sketch
