To keep elastic from getting stuck in the seam allowance as it’s inserted, use fusible web or machine-basting to anchor them to garment within the casing area. Be sure to remove basting after casing is finished.
Do the machine basting but do not bother with the fusible web option. For experienced sewers I can’t imagine this step is necessary (I’ve never done it before) but I think it’s worth doing if you’re a beginner. A basting stitch is much longer than a regular stitch as its purpose is simply to hold something in place temporarily, so if you’re using a stitch length of “3″ increase the length to “5″ or something equivalent. It makes it much easier to remove the stitching later.
There are directions for making a drawstring out of your pants fabric but on the pattern envelope it calls for twill and elastic which is what I did and frankly – if you’re new at this you will want to do the twill version. Which they don’t exactly mention in the instructions. Just skip their step 7 and for step 8 – I’m replacing “drawstring” with “twill”.
Cut a piece of elastic the length of back elastic guide. Pin each length of twill to one end of the elastic, overlapping ends by 5/8″. Stitch overlapped ends together securely in a box, as shown.
The “back elastic guide” will be indicated on the pants pattern piece. For the twill: I cut the length the pattern calls for in half. If the ends are way too long when you wear your pants you can easily cut them shorter.
Insert twill and elastic through one buttonhole opening in pants front casing and out remaining opening so that lapped ends are at the side seams and having ends extend evening in front. Distribute fullness evenly in back waist. To keep casing flat in the front area, stitch in the ditch or groove of side seam. Knot ends of twill tape.
Patience help us with commercial patterns! They do not tell you how to get that twill into the casing and I promise it does not magically slide on through. Fold the edge of your twill back and put a safety pin through it – as big a safety pin as will fit through the button holes.
Push the safety pin through the casing. You will have to inch it through, it’s a little tedious. When you get it out the other button hole you can follow the rest of their directions.
They don’t mention it, but now you can remove the basting stitches if you used them.
You can knot the ends of the twill tape but I would trim it in an inverted “v” instead.
Because now you need to press the crap out of those pajama pants! After this you probably won’t ever press them again but a really good pressing at this point will set all your seams and hems to behave well.
NOW you’re done!!
What’s next? Once you’re completely done you need to take a picture of your pants to share and email me the jpeg at firstname.lastname@example.org. Once I have gotten all the pics I will share them in a post and then I will randomly pick one of you to get the pair I made.