Here is my non-turtle version:
it's based on MFR's mob counter. when there is a mob entity in it's range it sends a redstone signal(although it did react to me so you might want to isolate this setup), which triggers lower block placer(openblocks), gets delayed triggers middle, and top after that. i used bundled cable from project red to minimize space required.
you also might have noticed Inverted Cell from project red, which invert signals from mob counter in order to trigger creation if there is no golem in the cage.
i tried using TE's activator instead of block placers from openblocks, but for some reason sometimes i got a snow where pumpkin should be even though top activator had only pumpkins, so i'm not sure what's up with that.
you can also use MFR's block placers, but because they work when there is no signal applied, you need to inver signal after delay.