3.4.3. How to place G1-3 in the Realms:
Buy "Giantcraft". Send the PCs up to the Ice Spires as the number of giant raids increase. Replace the giant steadings of Hartvale with G1, G2, and G3.
Eric Boyd's ideas for setting G1-3 in the South:
a) There are known hill giants in the Tejarn Hills of Amn and the eastern Small Teeth. I would place G1 there.
b) Frost Giants are unlikely to come this far south. However, if they do, they probably live in the Snowflake Mts., the Cloud Peaks, or the Giant's Run Mts. I would probably pick a remote part of the Cloud Peaks or skip this part altogether.
c) Fire giants probably live in the vicinity of a volcano. That suggests the twin peaks known as Kossuth's Eyes in the Small Teeth might harbor a fire giant hold.
If you do all this, I would suggest linking G1-3 to the Sythillusian Empire troubles. The hill giants are already part of this, simply have the frost and fire giants be part of the monster armies besieging Amn.
If you decide to add D1-3 to this as well, I would have the drow be from Guallidurth (under the Calim Desert, mentioned in DDGttU) or from Karsoluthiyl (off the coast of Baldur's Gate, under the sea floor, mentioned in DDGttU). I would probably pick Guallidurth, and tie its actions back to the Night Wars (see the history section of LoI and EoSS).