Arrows show where to point the towers. Stack 1 and 2 are pointed a tad more west than south. The biggest slowdown for this map are the western wyverns that fly up and hide around the side rather than going directly to the crystal.
Forest Golems are positioned so that they intercept Ogres and their balls.
Towers at hints 1, 2, and 4 will take damage, but will be fine if your builders have enough tower health. The combination of the auras with the Forest Golem will keep things nice and safe.
I put App/Huntress Summoners on all stacks. For efficiency, having summoners on just stack 1 and 4 would probably be best. I just like making sure that my survival builds can consistently handle 4 summoners to ensure that they are solid.