Holding the waves alone, without thralls 
. Building maze is my suggestion and i did it only for this purpose. The Aoe of war axe, the poke of spear make you invincible on narrow paths.
Send a photo please 
. I have to finish this…
In this case narrow path works but the demolishers are giving me distraction and the absence of stamina is making it even harder.
Thank you for your feedback 