I got some thick, adhesive-backed weather stripping at my local home center store and used it to ensure an air-tight seal between the leaf blower and the wood disk. Caulking would probably work better, but I wanted to be able to remove the blower easily when I needed it for yard work. If you have a leaf blower you are willing to permanently dedicate to this application, then caulking may be the way to go.
Then I used long wood screws and washers to hold the blower down on the wood disk. My model of leaf blower has convenient tabs on the edges to run the screws through. It only takes a couple of minutes and a screwdriver to free it up when I have to use it for yard work.