Too easy, you just have to create snipers in conjuction with the radars, or missile launchers and radars. It'll occupy the whole map, the enemy won't get far from their entry point. You'll just have to go afk and wait for the level to end
Try my course, its name is Battle Royale Tower,...if that doesn't work my account name is ur7xll009....the course is based on the manga and live action movie Battle Royale