"plain area" is correct and usable in written English.
You can use it to refer to a flat, featureless area of land with no plants or structures. For example, "The farmer looked out across the plain area, noticing that the soil was sandy here."
Jæren, lowland plain area, southwestern Norway.
Silty alluvium covers most portions of the North China Plain area of the province.
The coastal plain area around the Llobregat river delta is under intensive cultivation.
Taliban forces won control of this village and others in the Shamali Plain area in 1999, and systematically executed citizens and burned their crops.
When a revolt broke out in the Atlantic plain area following the capture of Marrakech, he conducted a methodical purge there in which more than 30,000 people were executed.
Its drainage area is divided from the Sungari (Songhua) River basin to the northeast by a belt of land that has been gently uplifted over geologic time, while the plain area has been gradually subsiding since the Mesozoic Era (i.e., for about the past 65 million years).
These coastal plain areas are dominated by sedges and cotton grass, and mosses including Sphagnum are common.
Further showers were likely to give river levels a "temporary upward blip" and flood plain areas would remain flooded, he said.
"The tulle was the base where the lace was appliqu? and then we cut away all of the tulle, so you had plain areas of satin organza.
"The tulle was the base where the lace was appliquéd and then we cut away all of the tulle, so you had plain areas of satin organza.
(a) Heating surface with coated and uncoated (plain) areas.
