Post Office Flat Spring is located in the Zuni Mountains portion of the Mt. Taylor Ranger District of Cibola National Forest at the intersection of FR-480. FR-548, and FR-612.

Cibola National Forest covers more than 1.6 million acres and includes mountains, grasslands, wilderness, and forests. The name Cibola comes from the Zuni word for their tribal lands, which the Spanish later translated as "buffalo". The forest is home black bears, cougars, elk, and pronghorn. Cibola National Forest offers many recreational opportunities including hiking, camping, fishing, hunting, and skiing. It also has cultural and historical significance, as it contains ancient Native American sites and historic trails.

The National Forest has four ranger districts: Sandia, Mountainair, Magdalena, and Mount Taylor. In addition, the Cibola has four wilderness areas: Sandia Mountain, Manzano Mountain, Withington, and Apache Kid.