These were the subclans descended from the Gileadites: The Iezerites, named after their ancestor Iezer. The Helekites, named after their ancestor Helek.
So the allotment on the west side of the Jordan was for the remaining families within the clans of the tribe of Manasseh: Abiezer, Helek, Asriel, Shechem, Hepher, and Shemida. These clans represent the male descendants of Manasseh son of Joseph.
Then the angel of the Lord came and sat beneath the great tree at Ophrah, which belonged to Joash of the clan of Abiezer. Gideon son of Joash was threshing wheat at the bottom of a winepress to hide the grain from the Midianites.
And Gideon built an altar to the Lord there and named it Yahweh-Shalom (which means “the Lord is peace”). The altar remains in Ophrah in the land of the clan of Abiezer to this day.
But Gideon replied, “What have I accomplished compared to you? Aren’t even the leftover grapes of Ephraim’s harvest better than the entire crop of my little clan of Abiezer?