Here's generally the way Zach and I approach writing an episode of Obituary:
Things usually start with talking out scenarios or character interactions that would prove fun. Once we've explored the ideas and settled on one, we talk out the beats. Zach is usually the one to take a first "Skeleton pass" where many (but not all of the bones) would be placed. I then take a crack at it, and after that initial volley we talk through what we're still missing or things we discovered while writing (for either the purpose of taking the episode in a different direction, or for the sake of storying or setting up a bit for later).
Whoever then has a better sense of what the script needs gets the next pass and then we send it back and forth until we're really pleased with the plot, jokes and flow.
As frequently as we can we'll both reconvene to breakdown and fine tune script elements. Sometimes it's finer minutia - we're even so silly to rephrase script directions - and other times our notes and changes are much larger than the actual piece we're working on; certain characters might be in need of certain elements later on, etc.
We're very big on looking big picture and so we've spent a lot of time on details that may never be seen. We've got a handful of comic books that June reads in this universe that we may never see, but those are helpful elements to us. Anyway, that was just a quick little look into how we approach Obituary; hopefully that proved somewhat insightful!