Secret tip!

If you see a hoard or tough enemies, place one block right in front of them. Wait till they attack it and go back to build mode. Then, place one on top of that. Build one block all the way around 2 high. Then, delete the first block as soon as they are all attacking. Done! The walls will be like a hammer crushing ants! Instant kill even works on enemy heroes!!!

F1stickman about Block Fortress: War, v1.2.4