For the Felicity Dress, I instruct you to use a lapped zip, but you are more than welcome to use an invisible one if that's what you prefer, or it's what you have on hand.
Before we start, you do not need an invisible zipper foot to insert an invisible zip. While it does make it easier, you don't need one. What an invisible zip foot does is open the zipper teeth out from the zip tape for your needle to stitch as close to the teeth as possible - but you can do this yourself with your fingers using a standard zipper foot and taking your time. If invisible zips are your preferred zip however, you might find it useful investing in one.
Below on the left is my machine's standard zipper foot and on the right is my invisible zipper foot. You can see that the invisible zipper foot has two channels running along the bottom. When inserting your zip, the teeth go into one side of the channel, which opens them up for a close stitch.
So, let's get started!
2. Open your zip and place it face down on the right side of the garment with the zipper tape in the seam allowance and the teeth along your pressed seam line. Pin in place.
Note - I aways find initially trying to figure out how to place the invisible zip counter-intuitive, but once you see how it's supposed to end up, it all makes sense!
3. When inserting an invisible zip, you want your stitching to get as close to the zipper teeth as possible by opening them up.
The invisible zipper foot does this for you, but if you're using a standard zipper foot, you'll need to open them out yourself. If using a standard zipper foot, you might find it helpful to gently press the zipper teeth out with a warm iron (you don't want it too hot, otherwise you'll melt the zipper teeth).
Start your stitching from the top of the open zipper tape, working your way to the bottom.
4. Stitch as close to the bottom of the open zipper as you can, then back-tack.
Because I was silly and used white thread (!!), you can't see my stitches that well, but here they are anyway.
And what it looks like on the outside...
5. Now we need to repeat the process for the other side. This is where you need to be extra careful that you are lining up your zip correctly, so that when it closes, your seam won't be out, resulting in unmatched sides (this is always where I run into trouble, so take your time!)
On this side I'm using my standard zipper foot, if you're doing the same, you'll be opening out your zipper teeth so that you can stitch as close to them as possible. Go slowly...
6. Now that both sides of your zip are attached, we need to stitch closed the bottom of the seam. Right sides together, pin them closed while pulling the bottom of the zip out of the way.
7. Using your standard zipper foot and starting from the bottom of the hem, stitch your seam closed, getting as close to the bottom of the zip as possible by holding the zip out and away from the seam. Back-tack at both ends.
8. Gently press your seams and marvel at your invisible zip!
Stitching in the first side is fine, but when it comes time to insert the other side, because I can't baste the seam shut first like I can with a lapped zip (which results in two perfectly lined up sides and a matching waist line seam), I always tend to slightly skew the other side of my garment. The waist seams rarely match perfectly, which I find annoying, and I always end up with a slight bubble at the bottom of the zip because the fabric isn't matching.
Any tips on how to stop that? Maybe I'm doing it wrong... perhaps practicing invisible zips needs to be on my list of sewing goals for next year :) Oh well, at least lapped zips work for me every time and I like them.
Do you have a zip preference?