(I spoilered the text relevant to the actual location and name of the island to hopefully avoid spoiling anything for players who want to completely avoid them for the new update.)
There is now an island named Ierochos that now gives clearstones outside of Othrys, and it doesn’t have that painful darkness. I think this might be a more efficient place to get clearstones overall, though you’ll get far more per run in Othrys than this place. It is at the very northern part of the Bronze Sea, just below the Pelion Rift.
i often just go in at day, do a othrys run, attempt to destroy poseidon’s temple make an offering at poseidons temple to get good luck on my next ds run, fail miserably, head back to my ship as it turns dark, start fishing, and when it turns day i head back into othrys again to do it all over