I usually use the cellar door and a ramp down to the bottom. Wandering hordes usually just walk on by since they are actually zombies. and there are no corners for them to get stuck on and attack The problem is the screamers dont bother with pathing in this case. They know exactly where you are...
With my preference for underground bases, seeing how screamers act now made me have to turn them off, as they are just irritatingly not zombie-like. They don't even bother with doors - open or not, they just know exactly where the heat comes from and start digging because they retain their...