To get a correct fit for doll clothes you need to make darts on the pattern to allow for any curved surfaces, especially on the bust or waist of fashion dolls which often have exaggerated features. The goal of the sloper is to to give you a basic pattern that shows the smallest point where seams can be made on fabric to fit a doll with non stretchable fabrics.
To Mark the Side Darts For the Doll's Bustline - Fit the modified sloper you made in the previous step back onto the doll with the shoulders taped or pinned to the doll's body and the waist line taped or pinned to the front of the doll. Mark the side seam near the waist, and fold a small triangular fold (facing down) to adjust the material so that it fits to the top of the doll's breast, in a straight line out from the side seam. Don't worry about any gaping fit at the waist right now, you only want to adjust the fabric to get a neat fit along the side seam under the doll's arm. Tape your folded dart in place and mark the side seam and the arm hole seam, just like you did for the back. Carefully trim the armhole seam away. Then trim away the side seam, leaving the extra material which is loose at the waist line, and leaving the tape holding the triangular dart in place. Repeat for the doll's other side.