How to tile around a Pre fab shower base
I have not worked with this particular base, but a typical installation would have globs of mortar underneath the base to keep it from sagging and bending under the weight of the person in the shower. That would help to keep the base where it belongs. The more I think about it, the more I realize that I have never seen a base without some means of attaching it. Are you sure that there is no specially made anchoring hardware that came with it? If not, maybe you can fabricate something out of flat stock steel, say 6" long by 1-1/2" wide, and 1/8" thick. Heat it up with a torch and bend it to look like a "J", and drill a few holes in it. Then mount these to the studs so that they catch the bottom lip of the base, and keep it from creeping away from the studs. Also, as a sidenote, is there any kind of channel or other means of keeping water from getting behind the unit?