I’ll not give many construction details as this waistband is most commonly used on jeans. Instructions abound in many patterns and on-line tutorials.
However fit is a subject I’ll weigh-in on. I grew up in the time of Bell Bottoms and Hip Huggers. Before TJ906 I struggled with fitting this waistband. OK, I also thought my body was wrong and the pattern was right. It’s only been the last few decades that I’ve been embolden by the Home Sewing Community with the concept “the pattern is only the beginning”. TJ906 includes detailed instructions on what to do to make this waistband fit. I needed to make several darts in the contour waistband pattern piece. I placed the wide end of the dart on the upper edge (waist side). I understand others (those with big waists and narrow hips), do just the opposite, ie wide end of dart is on the hip side of the waistband. You can also slash and spread if the waistband is just not long enough and of course make tucks if it turns out to be too long completely.
My pattern calls for placing the center back on the fold. I’ve added a 1/4″ seam allowance and cut the center front on the selvage. It find the on-the-fold cutting layout is a fabric hog. I’ve also seen two -piece contour waistbands i.e. a center back cut on fold and a front cut double; then all the pieces seamed together at the side seams. I may develop and share that version just because it is really fabric conserving.
Whichever style is cut, 2 are needed. One for the waistband and one for the facing. I also cut 2 sets of interfacing. I like a firm waistband. I have not but understand others tape the upper edge. I fuse interfacing to the waistband and then recut to match the original pattern piece. I’ve been satisfied with that procedure but have had a few fabrics that would have benefited from the addition of stay tape. Belt loops and belts saved those pants.
For fabric conservation practices, i.e. I’m cheap and like to buy the smallest length possible, I cut the facings from a second piece of fabric. I find this to be a good use for remnants especially if I’m able to use a slightly lighter weight fabric like the dress linen in the photo above. (Quilting cottons and shirtings are my other favorite choices.) The lighter weight makes it easier to fold the facing and wrap it around. I also prefer the triple zig-zag stitch for under stitching. It may indeed be the reason I don’t notice the lack of stay tape. To understand the superiority of the triple zig-zag to the usual straight understitching, well, you have to try it yourself. It really does seem to persuade the facing to roll and stay on the inside; and while it allows a little stretch that upper edge is firmed.