Notch all your seam allowances, balance marks and the center fronts. Mark the darts using a hand sewing needle and thread, leave the threads reasonably long so when you separate the pieces you will have plenty of thread left over. Now remove the pattern pieces carefully and pin the darts with right sides together. Take the neck and armhole facings and pin together at the shoulder seams. Go to the machine and stitch the darts on both the front and back pieces. Take out the thread used to mark the darts. Neaten the two center back seams using a zigzag stitch or an over locker.
Now we are going to sew in the invisible zip, the tape at the top of the zip should sit at the edge of your neck edge, that is why the zip tape sits above where the zip closes, it is a good guide. If you have not put an invisible zip in before, it is best if you start by; placing the zip right side up on the seam allowance it will be sewn on to. Now undo the zip and roll the left side of the zip over onto the seam allowance, so you have right sides together of the zip and the dress. You will have the zipper foot on the left edge of the zipper teeth, so you can stitch up against the teeth with the tape rolled out.
Now stitch all the way down to the bottom of the zip as far as you can go. Do the zip up to check the stitching. Undo the zip again, match the tape at the neck edge on the other side with right sides together, and stitch all the way down the zip on the other side. We are sewing in the zip before we actually put the garment together, because it is a lot easier to deal with just the center back while you are putting the zip in. Don’t worry if you don’t finish exactly opposite where you finished on the first side as long as it is close, that’s OK. Do the zip up and check that your neck line is matching.
Now to finish off the bottom of the zip put the right sides of the seam allowances together, and pin at the bottom of the stitching of zip. Make sure you match both sides and start where the highest point of the stitching finished if they don’t match perfectly. Make sure you reinforce the beginning and the end of this stitching line. You will still need to use your zipper foot so you can stitch up against the zip. Stitch on the seam allowance line all the way to the hem, pat your self on the back, it is not easy! Sew your shoulder seams of the facing on the seam allowance line. Take the contrast panel piece and bag out the hem by stitching with right sides together. Trim the seam allowance back and turn through to the outside. Go to the iron and press your darts toward the center front and center back respectively. Press the contrast panel into position on the front of the dress. Pin at the shoulders and neck edge.
Press the shoulder seams open on the facing. I have cut the end of the zip off because it was too long, once you have sewn your zip into place it is safe to do this but do not do it before you have sew it. With right sides together pin the front and back shoulders together. Go to the machine and stitch both these shoulder seams. Stay stitches the front contrast panel onto the dress, at the neck edge to hold in position while you sew the facing onto the dress. Now take your facing and with right sides together pin around the neck. Go to the machine and stitch on the seam allowance line, make sure your shoulder seams are open and that the seams match where the zip does up. Trim the seam allowance back by half. Press the seam allowance under the facing and stitch close to the neck seam you have just sewn, this is called stay stitching and helps hold the facing back. Go to the iron and press the facing into position, check that the armhole seam allowances of the facing don’t protrude past the front of the dress.
Now place the dress down on the table with the right side up, roll one armhole up like a sausage into the other armhole. Pull the casing around to encase this roll and pin the facing around the armhole. Go to the machine and stitch this armhole seam leaving a few centimeters or an inch, not sewn at the beginning and the end of each seam. This will allow you to sew your side seams up later. Trim the seam allowance and pull the dress through the tunnel. Repeat this process for the other armhole. Pin the contrast fabric to the side seam and stay stitch this into position. Pin the front and backs together at the side seams making sure you have right sides together. Stitch both seams on the seam allowance line. With right sides together pin and sew the facing side seams.
Now with right sides together and matching the side seams pin the facing to the dress armhole. Stitch this section around to match the stitching you did previously when you bagged out the armhole, and trim to match the rest of the armhole. Neaten the outer edge of the facing by zigzagging or overlooking. Turn the facing back over the zip at the center back neck edge and stitch down onto the tape of the seam to bag it out. Turn through to the outside. Go to the iron and press the facing and side seams making sure the facing is pressed well back. Turn the hem allowance up and pin it into position. If you have not neatened the hem before do so now. Then sew the hem up by hand using a hand sewing needle and thread, give you garment a final press. Well done!