My ideal work day? I'd wake up without an alarm but I'd most likely wake up early because I was excited to begin working. Whatever the job was would involve being outside at least part of the day. The task would have a clearly defined objective, wouldn't be overly difficult, and would provide immediate gratification in the form of knowing how much progress had been made. I would become so engrossed in the work that I'd lose track of time. That's the key, when the day just flows and I'm lost in the work. I'd take breaks when I want, eat when I want, stop when I want. Unless I was physically exhausted I would probably stop as it was getting darker because I'd be enjoying myself so thoroughly that I wouldn't really call it work. Maybe I'd throw a run in there somewhere but most likely I've met my exercise quota just doing what I was doing all day. Maybe I'd take a run anyway, because I like to run.
Assuming it were possible to find a job like that with complete autonomy over when I started, stopped, etc. I'd probably do it for minimum wage or there abouts because I don't really need to build my stash any more. If I was FIRE'd I'd do work like that for free, because it's not work to me, and because that's the kind of day that makes me feel alive, and thankful for being alive.