You guys are overcompilcating this, quite a bit. I have done this
several times, and if you use enough spackling to glue in the sheetrock
hole it will stay in place without any metal clips. The trick is not
to even try to get it even (flush), you want slightly in, like 1/16th
or something like that. Then after it dries you can fill in the 1/16
and sand until it's flush with the rest.