Flat is related to Wall. Wall is the opposite of Window. 
Paper is related to Daily. Daily is related to Weather. Weather is related to Overall. Overall is similar to Gross. 
Flat <--RelatedTo--> Wall <--Antonym--> Window 
Paper <--RelatedTo--> Daily <--RelatedTo--> Weather <--RelatedTo--> Overall <--SimilarTo--> Gross 