If you are sewing the post Edwardian pattern then you need to simply sew a plain seam and stay stitch the allowance in place. Start by placing the two pieces together, face-to-face, and sew a seam 1/2 inch from the edge of the seam allowance.
Press the allowance to one side. On the corset used to make the pattern all the seam allowances were pressed toward the center back.
Next, the seam allowance is graded to reduce bulk. Trim the seam allowance in half.
The side of the allowance that is closer to the exterior of the garment is trimmed in half again.
Then sew once more, 1/16 from the seam.
If your stay stitch is closer to 1/8 from the seam that's OK too. The finished seam will look like this from the right side.
And this from the wrong side.
The raw edges will be covered with bone casing so that's all there is to do. Not bad, right?