Creating the Boning Channels
This pair of stays will be front lacing, so I folded the stays at the front panels. The back panel is open and in the center of the photo below. It is now two layers of material thick.
I lined up the seams and pined them together before stitching along the seams to secure the layers together.
I determined the very center of the back panel. Then I used a rolling chalk marker to mark a vertical line 3/8” from the center line. This is where I stitched the first boning channel seam. The channel is barely wider than the boning, ¼” wide.
After stitching both sides of the first boning channel, I marked another line 3/8” from the center back. All boning channels are created in mirror on both halves of the stays.
The next channels out are 3/8” from the other side of the tabs, and parallel to the first channels.
The next pair of channels are 3/8” from the seam between the panels.
The boning channels for each remaining tab are all parallel, and 3/8” from the edges of the tabs.
After all of the tabs had boning channels, I added the boning channels to the front of the stays.
I pressed the front panel so ti had a crisp front edge, and then stitched a ¼” boning channel along the front side. A ½” bone can be used instead if you prefer.
Leave a gap wide enough for your grommets. I use #0 grommets, so I left a 5/8” gap. After lining up the stitch line for the front boning channel, I mark the width using a Sharpie pen. Sharpie can be removed from most hard surfaces using rubbing alcohol, but test your machine before marking it to be sure the ink is removable. Alternatively, you can put down a strip of masking tape and mark it instead.
I recommend inserting a wide strip of twill tape or tailors tape along the area to be grommeted, to help re-enforce it and prevent tearing when the garment is worn.
Mark both sides of the 1/2 ” boning channels using a rolling chalk marker. This will allow you to make them consistent widths, and placed the same on both sides of the stays.
The centermost ½” channels are vertical. The others are fanned out across the front of the stays.