I feel like if the interruption amounts to "Are you free right now?" -- "No.", it's not that concerning. It shouldn't be that difficult to build the expectatio

I feel like if the interruption amounts to "Are you free right now?" -- "No.", it's not that concerning. It shouldn't be that difficult to build the expectation that if you're in the study, no one should expect you to be free, and if you're out of it, eg taking a break, then they can. But this particular issue seems trivially resolvable, as long as you manage expectations appropriately. In my own experience, my dad randomly worked from home (mainly when his day consisted of calls), and I just never assumed he was free; at least in the sense that I quietly asked, and naturally expected a "give me 10 minutes", and waited an hour before bugging him again.