First this is how I usually do it, and probably how you do too.
The circle of elastic is sewn into, well a circle, and pin and marked in quarters. The quarter points are also marked on the garment. The elastic is then stitched/zig zagged/serged to the top of the waistline, stretching to fit between the quarter points. It is then turned and flipped over and top stitched from the right side.
The issue with elastic always of course is that the more stitches you put into it the more it can lose its shape. I have inserted more than my share of bowed out waistbands.
What the Ottobre pants pattern instructions suggested instead was that the circle of elastic was pinned to the inside of the garment at the quarter points and that vertical basting length ditch stitching was added at each of these (which on the pants meant centre front, back and each side seams) and then the elastic was flipped to the inside and topstitched down at the casing line. I used my coverhem which I am trying to use as much as I can these days to increase my comfort level.
Note there was no first line of stitching to attach the elastic to the top of the waistline, only the final stitching of the casing. This eliminated one whole line of needle holes in the elastic and I found that the lines of basting were far more effective at holding the ring of elastic in place than pins, which can move into the diagonal and shift the elastic pretty easily.
Definitely this is the method I will use again, particularly with the coverhem- it was nice not to worry about pins.
Learn something new everyday. Particularly if you sew