Gigas and Carcharodontosaurs are a rare spawn on any map in Ark Survival Evolved, and on the Fjordur map, they seem to be even rarer, at least in my singleplayer world. I mostly find the Fjordur gigas in the highlands area, they have also been reported on the volcano. My favorite spot is near the beach at around 45.8 95.4. I have set up a trap made of metal behemoth gates at the base of a cliff. You could probably get away with a cheaper build, but I like the gates. Gigas and Carcharodontosaurs share the same spawns.
Fjordur Giga Spawn Coordinates
|Giga Spawn Locations on Fjordur
If you are looking for resources check Fjordur Resource Locations for more info.
Giga Tame Gameplay Video