4. Attaching the lining
Place the Front Lining piece and the Back Lining piece together with the right sides touching and the raw edges lining up. Sew along the shoulder seams. Iron the seams open.
Use a vanishing fabric marker to find point A as shown in the picture – this is the corner of the V shape on the finished garment where the two collars should meet. Point A should be on the central line of the back piece.
Use the fabric marker to mark the sewing lines at the bottom of both collars. The ends of the sewing lines should meet at point A. Pin to secure.
Trim off the corners of both collars as shown in the picture. (Note: the corner in solid red is from the collar laying on the top, and the corner indicated by the unshaded triangle is from the collar laying under and therefore covered by the other collar.)
Place the dress lining and the dress main pieces together with the right side touching and the raw edges lining up. Sew around the neckline. Make sure the seams on the front piece of the main dress go toward the side seam while sewing.
Turn to the right side to check whether everything has been sewn properly, especially the bottom of the V shape where the collars meet.
Clip at the angle points as shown in the picture.
Separate the lining and the main dress with the seams flipped toward the lining. Topstitch around with 0.1cm or 0.2cm seam allowance on the lining. This will prevent the lining from showing. (Note: do not sew on the main dress. The lining and the seams underneath should be sewn together at this step.)
Turn to the right side and iron the dress, especially around the neckline.
5. Finishing the armhole
Lay the dress open as shown in the picture.
Take one side of the dress (including main and lining) and roll it up towards the other side.
Keep rolling until you reach the other side of the shoulder.
Separate the main from the lining on the other side of the dress, and flip the main over to cover the roll.
Take the lining from the other side, wrap it around the roll, and meet the main dress with their right sides touching and the roll sandwiched in the middle.
Line up the armholes of the dress main and the lining and sew along the curve. Be careful not to catch the roll in the middle while sewing. Clip the seam along the curve.
Now gently pull the roll out from the front side of the dress through the shoulder tube.
The dress should be now on the right side with one armhole finished.
Separate the lining from the main dress at the armhole with the seam towards the lining. Topstitch with 0.1~0.2cm seam allowance on the lining side from the bottom of the armhole to as far as you can go. Iron the armhole areas.
Repeat with the other armhole.
6. Finishing the dress
Lay the dress open flat with the wrong side facing up, and separate the lining from the main. Finish the side seams with an overlocker as shown in the picture. Repeat the same with the other two side seams on the other piece of the dress.
Turn the dress wrong side out. Separate the main and the lining. Line up the side seams of the lining front and ling back, and the side seams of the main front and back. Sew along the side seams as shown in the picture.
Turn to the right side to check whether the pleat under the armhole has been sewn properly. Adjust if necessary.
Open the side seams and iron flat.
Hem the dress lining by either overlocking, folding up 1cm and sewing to secure, or folding up 0.5cm twice and sewing to secure.
Line up the side seam of the lining with the side seam of the main dress and pin to secure. Sew a few stitches to attach the lining to the side seam of the main dress only (i.e. the stitches will not show on the right side of the dress).
Flip one front collar to the opposite side and sew 0.1cm from the seam as shown in the picture. You will be sewing the front main and the front lining together so that the lining will not move while putting the dress on. (Make sure the stitches will be covered by the collar once flipped back in place.)
Hem the bottom raw edge of the dress: turn the raw edge 0.5cm up and iron. Then turn up another 1cm and iron. Sew closely along the folded edge.
Congratulations! You have now finished the petal collar summer dress.