If you are reading reviews from the other unmounted stones then this is probably getting a bit repetitive but not everybody checks all the options. My stones arrived very well wrapped in foam sheeting. To remove the old stone you can gently grab it in a vice on the aluminum and heat it from the bottom with a blow torch to loosen the glue. If that seems dangerous you can also put it in a pot of boiling water for a bit then remove it with tongs and scrape the old stone and glue off with a scraper of some kind.
To mount the new stone 3M Super 77 spray adhesive is what is recommended and what they use at Edge Pro. Putting paper or cardboard under the stone and blank to catch overspray is a good idea. Spray both the back of the stone and the aluminum blank lightly then wait 15-30 seconds for it to get tacky and press the stone and aluminum base together. Be careful to line them up fully before pressing together. Put something protective like waxed paper over the stone and set something like a decently heavy book on top for a few minutes while the glue bonds and cures.