
I will start off with a warning that I began filming with one Very Clear Idea for how I was going to explain underwear-sewing methods to you guys, and then I totally changed my mind. But! It’s for the good of the fit in the end, rather than the ease of applying elastic. Your preference may differ! I think my edit came out so that it wasn’t so confusing (I hope???) but anyway, I’ll explain it (hopefully) more clearly here as well 🙂 Here’s a link to the video up on my Youtube channel!
Out of all 10 patterns, 9 of them were constructed in one of two ways. There was one wacky exception (looking at you, Rosy Ladyshorts), but the other patterns were either cut as three pieces (a front, a back, and a gusset piece that is not visible from the outside) or four pieces (a front, a back, and two gusset pieces, one of which is visible from the outside). I have, cleverly, nicknamed the methods for constructing these panties the 3-piece and 4-piece methods and it really only makes any difference when you’re connecting the front and back pieces to each other (and, to a lesser extent, when applying elastic to the legs).
3-Piece Method:
Sandwich the pieces along the back seam as follows:
- Gusset, right side up
- back piece, right side up
- front piece, wrong side up


Pin and sew the seam together according to the pattern’s seam allowance. Grade and reinforce the seam if necessary. Once you flip the gusset piece forward (to overlap with the front piece), you’ll have a nicely enclosed back seam.

4-Piece Method:
Sandwich the gusset and back pieces along the back seam as follows:
- (bottom to top)
- Gusset, right side up
- Back piece, right side up
- Other gusset, wrong side up (**This piece will be visible from the outside, so if you’re using different fabrics, keep this in mind!)

Pin and sew the seam according to the pattern’s seam allowance. Grade and reinforce the seam if necessary. While the gusset pieces are still folded backwards, roll up the back piece out of the way. Lift up the gusset piece that’s on top and slip in the front piece. You’ll sandwich these three pieces, aligning the front seam as follows: (this will seem familiar)

- (bottom to top)
- Gusset, right side up
- Front piece, right side up
- Other gusset, wrong side up


Pin and sew the seam according to the pattern’s seam allowance. Grade and reinforce if necessary. Then, flip out the front and back pieces from inside the two gusset pieces and, ta da! You have two nicely enclosed seams.

Now, here’s where I changed my mind.
You can do two things here:
- Sew up the side seams, then apply elastics
- Or, apply elastic on the legs, sew the side seams, and apply elastic on the waist
Initially, I was all set on doing the latter. What’s the benefit? With this order of construction, you can apply the elastics to the legs in a straight line, without having to worry about making a loop of elastic and applying it to a circle. With this way, you can connect the leg elastic together at the same time as you sew the side seams.
But, this way makes it tougher to adjust the side seams in a clean way. In the last video in the series, you’ll be able to see what I mean by this with the Celeste bikini that I made. They ended up too big, but after taking in the side seams, they no longer matched. If I didn’t have the elastic on already, I could’ve trimmed the fabric away so that it looked better. Plus, this way leaves slightly bulkier sides from the edges of the elastic.
Sewing up the side seams first allowed me to try on every single pair of panties and get an idea if I needed to adjust the sides for a better fit. It also allowed me to note how much tension I might want on the legs and waist. If the legs seemed quite loose, then I knew I should put a bit of extra tension on the elastic to make them more snug. (This will also depending on how you prefer your underwear to fit.)
But sewing up the side seams first then means that I have to join the elastic together in a circle in some way. I chose to do a sort of lazy method, and just overlapped the elastic on itself when I finished sewing around the leg or waist. You could also, if you know exactly how much elastic you’ll use (and some patterns did provide this measurement, but I ignored it), sew the elastic together into a loop and then sew it onto the leg or waist. Again, it’s more about which order you find most comfortable!
Also, it feels necessary for me to shout it from the rooftops. Applying elastic KINDA SUCKS! Sewing underwear can be a quick and easy scrap-busting project, but the gosh darn elastic can be tricky! My advice is: keep going! No really, just keep trying! Practice practice practice. Especially if it’s your first few pairs of underwear (or a bra), your elastic might end up wavy or stretched out or just plain crappy. You will figure it out! I’m not a crafty genius for getting it (mostly) right myself, I’ve just made a couple dozen pairs of underwear already. And it’s the most time-consuming part of the whole project. Like, imagine. You tape together a few pieces of paper, cut out less than a meter of fabric, sew up three or four seams, and you practically have finished panties! But… then… literal meters of elastic have to be applied to three places, sometimes with two passes of stitches! And trimming the seam allowance? Oh my gosh, neverending.
Except, it does end. Eventually, at least. Just keep going and you will have your awesome new underwear in no time!