Laying out one large piece of sheet flooring to fit into a room that is not square is not always easy. I like to first find the wall that is the straightest, or the one that will be the most visible if there is a pattern on the flooring that will look crooked against an odd angled wall. That wall becomes my baseline.
Then somewhere near the centre of that wall, I draw a line perpendicular into the center of the room. This becomes the trunk of what I call my measuring tree. From the base line and this trunk line, I take measurements of everything I need to cut: the other walls, any obstacles in the floor, any counter edges, etc. I simply draw all of that out, right on the sub-floor, complete with all my measurements. That way, I can always check back to see what was where. Then I copy the 'tree' to a piece of paper.
Then I lay out the large sheet in another room, large enough to lay it out completely flat. I do not like to work on the back side because having to reverse all the measurements always leads to errors, and I don't want to waste the sheet or have to go to lesson two: splicing sheet flooring. I lay down masking tape for the baseline as well as the tree line and even put masking tape anyplace I want to mark or draw. Now don't make the mistake of working with a felt pen because it will bleed through the masking tape. Use a dark pencil and transfer the drawing.
This will quickly get you a good match for cutting the sheet flooring and having it fit well. Remember that the quarter round is there specifically to cover up the little bit that you just couldn't get right.