I’m using carpet to create a custom rug for our great room. 9 x 12 is way too small. My dilemma is this: we have a fireplace with stone surround on the floor that comes in approximately 2 feet and a bay window. When deciding on size- how do I measure? 16” from all sides of room? 16” from where the stone surround stops? Do I exclude the bay window and measure from the wall?