Sentence:  Instead of isolating the literal flatness by specifying and <WSD>circumscribing</WSD> it , the pasted paper or cloth releases and spreads it , and the artist seems to have nothing left but this undepicted flatness with which to finish as well as start his picture . 
Meaning of the word marked with <WSD> tags:  restrict or confine, "I limit you to two visits to the pub a day"