My solution is to simply follow my old student cycle - "lecture time" from 9am to 1pm, lunch break from 1-2 (if you want a hot lunch as I do, it always triggers

My solution is to simply follow my old student cycle - "lecture time" from 9am to 1pm, lunch break from 1-2 (if you want a hot lunch as I do, it always triggers an interrupt regardless). Since lectures are almost never contiguous, you can slot meetings and speculative meetings between them. I often meet people for lunch (the equivalent of "for coffee") and put important meetings at 2pm - 3pm (so that they stand out in my schedule, but still don't break my contiguous day.) Everything important happens at 2/3pm onwards. I often go for a run at 6/7pm (hint: exercise is important) but I usually do a lot of thinking while on the treadmill, so it counts more as "retreat and reassess time" than an interrupt. Peak time is 8/9pm onwards, since the run provides time for reflection and restrategizing. I view the next few hours as a "runway" in that it provides a time for loading things onto my mental stack. If by midnight things aren't flowing, I wind down and get to bed by 1am to prep for the next day - but if things are in flow, I unleash and never stop until I'm exhausted (anywhere between 3am - 8am) and crash. (This is why important meetings are kept for 2pm, so that recovery is still possible without constraining the runway)