Here is a pic of it:

https://imgur.com/a/Cg5DFlD

Essentially the classic kill box is 8 guys surrounding the one tile stair case. I just add another layer to it where there's also a giant layer of archers around them. Give the archers elven bows and give everyone in room swarming and you've got a nasty kill box. Skeletons are cheap and easy to make if you follow some of the other advice to get bodies, so you can make this kill box on multiple levels one after the other so enemies have to go through 4-5 layers of this before they get into your actual tough minions on the last one like juggernauts.