2-3 dozen is usually lots for the start of the season. Flocks where I hunt are mostly still locals, so total flocks are maybe 2-300 birds. Sometimes birds are still in small 6-8 bird groups at this time, so I spread them the groups out a bit more, with a distinct separation between groups, still in a sort of broken U setup. Not sure if you really need to do that, but that is the way I see them feeding quite a bit it the field. Later in the season, I set the same as the others suggested.
Little hard to see in the pics, this was an early season shoot, set in groups.
