How to Sew a Placket
The new Shona Romper has a snap placket on Version 1. To make plackets easier, here are some step-by-step photos and instructions. I'm using woven fabric for clarity but the same method applies to knit fabrics.
Plackets, welts, double welts, single welts, and facings all basically work on the same premise. They're a bit scary at first and often pattern markings do not help with the anxiety. Pattern markings often make it look like you're doing some blind sewing on markings you then cover, hope you hit them, then cut a hole in your good fabric...riiiight. So hopefully I can clear some things up for you and make sewing plackets or welts less scary. For the purposes of this post, I'll say "placket" throughout but know this is interchangeable with "welts" and it's the same process with an extra triangle (you'll see.)
First, plackets are a formula. You don't need to know this, but for some people, it helps to visualize. For the purpose of this visual, I'm going to ignore "turn of cloth" measurements. Meaning, use the placket pieces drafted for the garment until you understand how this works. Your pattern maker *should* have drafted the placket pieces to include any width taken up by thickness in turning your fabric. If fabric had zero thickness, this would be your formula. If you're sewing with boiled wool, for example, this would need to be altered.
Each placket piece needs to be 3x the width of the hole you are creating. So, if the entire width button hole is 3/4", each placket piece would be 2-1/4" wide. Once folded in half, each side, butted up against your cut line, would be 1-1/8" wide. This allows for 3/8" seam allowance on each side, leaving 3/4" to overlap on the hole. If you were creating welts, your seam allowance would equal each folded half so they butt up against each other on the fold.
I know. This is very abstract. Here are some pictures.
The placket pieces are laid in the place for the neck opening, raw edges butted up against each other, right sides together. Pin or use WonderTape to keep in place.
Starting at the top, sew 3/8" from the raw edge. At the stop point at the bottom, plus or minus 1/8", make a decisive 90 degree turn. These 90 degrees and being decisive will make the rest of it so much easier. Go to where you'll be 3/8" from the opposite raw seam and make another decisive 90 degree turn to sew back up to the neckline. These 90 degree square angles are imperative to getting a good, pucker-free turn.
This is what it looks like from the WRONG side. No back-stitching or over-stitching on those corners allowed. Decisive 90 degrees.
Cut right down the center between the two raw edges until about an inch from the bottom. Often pattern marks only give you 1/4-3/8" here. I'm telling you to take more. Cut nice long, acute angles all the way TO but NOT THROUGH your 90 degree turns.
Don't clip your sewing, but don't come up short either. This is the only other scary part.
You can do it.
Check your cut from the wrong side. See. You did good.
Back to the right side. Start pressing the placket pieces towards center. Doing this little bit of pre-pressing before you push the placket all the way through makes it a bit easier to push through.
Push the placket all the way through to the wrong side. It's going to resist. You're going to doubt yourself. Don't doubt yourself. Make it go. Use steam and press little by little and make it lay flat. Then put the iron flat on top and give it a good final press. Let it cool in place.
See your little triangles that went too? See how nice and long they are and how easy they will be to catch when you top stitch, or if this was a welt pocket and you were going to attach a pocket bag? So much easier than teeny tiny tabs.
Check your work from the front side. Did you get little puckers? Can you steam them out a little bit? If you have big puckers, make sure your 90 degree corners were 90 degrees and you cut all the way TO those corners. Make sure there were no errant stitches past your corners. Is it flat enough that when you top stitch it will behave? Ok, carry on.
Back to the wrong side. You're going to leave your seam allowance flat against the wrong side, but now you're going to iron your placket sides back to cover the hole, over lapping each other. Do one side at a time.
Pin the plackets together, and top stitch from the front around the placket. Choose a stitch or twin needle wide enough to catch the seam allowance on the wrong side. This is the only blind sewing you really need to do in a placket and use the easiest option available to you. I like a nice wide 3-step zig-zag on knits.
Check the wrong side. Did you catch your seam allowance and your little triangle tales? Of course you did. You are a badass. Now get up and do a happy dance.