Star movements probably. They also knew how long certain things would burn for. There were even candles that would be marked specifically for hour counting.
Yup, the ancients loved stars. It was strangely common for multiple cultures to create these weird observatories that were mostly for observation of a single star associated with different seasons.
Mechanical options were usually used by people trying for some form of efficiency either social or to mark distance. Marking time on ships was very important for accurate mapping for instance.
As for most of society meeting up at a given time just took longer as everything was more of a rough estimate. Some of the accounts have been guessed at as people didn't write details about how they approached time down. It's been hazarded that the day marked your doing productive stuff period and you set out your routine for days in advance so people knew where to find you if not exactly when you'd be doing it. Evening was your social planning time where you'd meet up and share details of your to do list with the people who needed to know.
I once spent a week with a whole bunch of people camping on a big property for a Medieval recreation event where we had volunteer work to do on the property and agreed to attempt to explore time as our ancestors knew it. We all ditched our watches for two weeks. It was actually generally fairly relaxing? Everything moved a little slower but not by that much. There wasn't any way to have much anxiety about not being precise so you just got used to people showing up during a wider span. If there was somewhere people needed to be around a specific time the person hosting the event just dispatched some runners to the places you knew people were going to be and people became more conversational as they passed along info. Actually very basic conversation had a lot more interest because passing along knowledge of what you knew was happening elsewhere became an actual topic of combined mutual interest instead of very boring comparisons of time tables.
It very much was! There were construction projects, games tournaments, arts... You'd think that the absence of clocks meant that people would be habitually miss things but I don't think people did more than usual.
I recommend it. Experiencing that kind of temporality made me realize how much the mass adoption of clocks impacts our experiences. I never expected the degree to which I would pay more attention to the people around me.