When I built my 2 star wolf & 2 star boar farm, I first determined that invasion events came from the north and or south of my base, so I built my pen to the east. Fortunately for me there was an abandoned red berry village to the east, so I built a massive earthen wall around that entire village. The area contained 3 outbuildings, a boar pen and a hunter's blind which I completely restored. I placed work benches inside the buildings as their distance from each other ensured near perfect workbench anti-spawn coverage. I also installed workbenches on or beside the earthen wall, as well as some out of sight up in the trees surrounding the area. I did end up having problems with one particularly bothersome Greydwarf Shaman, but I staked out the area one day to find out where it spawned, and placed a ward on the exact spot it spawned. I also installed wards underground beneath each gate entrance. I only ever find deer parts within the enclosed area. I do have a fence separating my wolves from my boars. The wolves have 2 separate breeding pens within their area, into which I place 2 when I want to breed them. I allow 8-12 wolves to mingle amongst the boar within their area, just in case something I have never witnessed happens.

I have never had a problem with spawns or invasions, other than one time an invasion raid from the swamp happened as my character was beginning the sleep cycle. As I generally begin my sleep cycle on the cusp between day and night, the swamp denizens had a good free-for-all against an undefended base. Fortunately because I keep my 2 star wolves and boar together they were able to defend themselves admirably, and only about a dozen tamed animals died. Having an invasion occur during sleep can only happen if the invasion occurs while one's character is in the cut-scene period as it begins to lie down before the screen goes black, so it is an extremely rare anomaly.