Those red boxes indicate where a hearthling (or anyone else for that matter) can stand when interacting with the entity IIRC.
I believe it appears like that from rotating the object as I’ve seen it happen before for other entities, though I’ve yet to throw up a report on this. Mostly because it’s just a suspicion at the moment, I’m gonna play around with it and see if I can come up with anything.
Alright, I’ve messed around with that idea and brought with me some pics to show for it:
They pretty much speak for themselves, notice though that it’s as expected only in the second image, the rest are showing issues. I’d wanna add that the images show for the carpenters workbench but the same results have been coming from the weaver’s workbench so it’s not just limited to that (and, I doubt, limited to workbenches even).
I think this is a more issue than just a minor one though, since this also affects collision boxes.