Apparently no one responded to this.
Flat Rock, Cherokee Nation, was the 1st Indian Expedition's camp/headquarters on the Ft Scott-Ft Gibson Road (aka Texas Road) and Flat Rock Creek. It is a few miles north of present Wagoner OK. What was the Grand (Neosho) River is now Ft Gibson Lake in this area and Flat Rock Bay now covers the lower mile or two of the creek on the west side of the lake. Old maps show the Texas Road bows to the west in this area, well west of the Grand and crossing the Cherokee-Creek boundary for a short distance.
The references to the Hay Camp Action where Co. K of the 1st Kansas Colored were massacred prior to 2nd Cabin Creek is the same vicinity.