[4] Flat Top Mountain is located 9 miles (14 km) east-northeast of Noxon, Montana, in the Cabinet Mountains Wilderness, on land managed by Kaniksu National Forest and Kootenai National Forest.

[2] Precipitation runoff from the mountain's east slope drains into Mill Creek which is part of the Fisher River watershed, whereas the other slopes drain into Rock and Swamp creeks which are tributaries of the Clark Fork River.

Topographic relief is significant as the summit rises 2,100 feet (640 m) above Ozette Lake in one-half mile (0.8 km) and 2,500 feet (760 m) above Wanless Lake in approximately one mile (1.6 km).

The mountain's toponym has been officially adopted by the U.S. Board on Geographic Names.

[4] Based on the Köppen climate classification, Flat Top Mountain is located in a subarctic climate zone characterized by long, usually very cold winters, and cool to mild summers.