Start with the the smaller north end of the building. Score the valley folds on the reverse side of the paper (as explained in Tips & Techniques), and score the roof mountain folds on the front of the paper. Cut out the pieces.
To make a straight long fold, place the fold line over the edge of a table or the sharp corner of a book or wood block. Press the paper over the edge gently to get the fold started, then crease.
Shape the angles of the roof to match the roofline of the sides. Then glue the sides to the tabs.