Finland is a "high trust" country, isn't it? I can't see this concept working working when > 10% of the population would game the system to get more "off-the-record" free time.
The flex hours are usually only for office workers where performance can be measured - sometimes it replaces overtime.
So the employer can "suggest" you work longer hours now when there's a ton of stuff to do (like end of year rush in accounting or payroll) and then you take days off when it slows down.
But yea, it's not something that's easy to police.
