You can place the farm anywhere within the ranges of the X and Z coordinates, but the Y level has to be precise. You shouldsubtract one from the highest Y coordinatethat you noted earlier. This will be the coordinate of your feet when you stand on the spawning platform of the farm. So...
2010. An Upper Palaeolithic flint and chert assemblage from Howburn Farm, South Lanarkshire, Scotland: first results. Oxford Journal of Archaeology 29: 323-360.Ballin, T.B. 2010. An Upper Palaeolithic flint and chert assemblage from Howburn Farm, South Lanarkshire, Scotland: first results. ...
To touch on the flint thing: There was one server I joined, general public vanilla, where the spawn area had been picked completely clean. I had to move out about a day's worth of time (luckily I found fuel for a torch) in order to find 1 flint. Only day 3, mind...