Indeed, you can legally fly under VFR (even without any flight plan at all)
as long as the weather is as prescribed in 91.155.

Similarly if you are in uncontrolled airspace.
There's less of that than there used to be, though.

Even in uncontrolled (Class G) airspace, VFR is permitted only if the weather
meets the requirements of 91.155. If the weather is below VFR minimums, you
can fly IFR without a clearance, but this is still IFR and must be in
accordance with the appropriate rules of Part 91, including fuel reserve,
cruising altitude, etc.

Barry