Where on the Sun does the slow solar wind originate?
In plain words
The slow solar wind could leak from the edges of coronal holes (dark regions of open magnetic field) or be released from closed magnetic loops when they reconnect with open field.
Precise statement
Determine the fractional contributions to the slow wind ($3e7\text{ to }5e7\,\mathrm{cm}/\mathrm{s}$) of (i) open fields at coronal-hole boundaries with large expansion factors, (ii) interchange reconnection releasing plasma from closed loops along the network of open-closed boundaries, and (iii) blobs from helmet-streamer tops. Use composition ($\mathrm{O}7+/\mathrm{O}6+$ ratio, $\mathrm{Fe}/\mathrm{O}$ enhancement of low-first-ionization-potential elements), Alfvenicity and magnetic connectivity mapping from Solar Orbiter and Parker Solar Probe. Answer: fractions with uncertainties.
What would settle it
In situ composition measured close to the Sun with remote spectroscopy of the connected source region for many wind streams.