This is a Trove guide showing you how to earn flux by soloing radiant giants in the sky realm and selling their radiant caches. The technique is pretty simple and relatively safe. You just need a decent DPS character (melee/ranged) with a good number of jumps, wings and a sky realm portal. While doing this, you can also do some dark heart dungeons for radiant shards and mine crystallized clouds to add to your profit. Happy hunting!
I tried this hole-in-the-ground strategy when I first started killing these, but it was on my Ice Sage. That's when I learned that it was possible for giants to fall through the island into the abyss. Ice Crash is not your friend.