I had most of the dress sewn, so I got down to serging.
At the gores, I folded the tip inwards so that I could serge the gore's seam allowance together with the dress' one.
At the fastening (front), I couldn't fold the tip inwards because it would be visible at the slit. I serged it and then folded outwards and overcasted with hand stitches.
I ironed fusible web on the edges of fastening and folded inwards several times. It should be as stiff as possible (the bodice shouldn't wrinkle when you lace it up tight) and I wouldn't have to serge it.
I made the lining piece for the neckline, ironed fusible web, serged and marked the line for stitching.
I laid it right side to the right side of the dress and folded the fastening edges once back (I unfolded the last fold). I sewed up to the edge.
Then I could turn it over, iron and sew a line of decorative stitches to catch the lining piece.
I didn't know how to serge a slit with open seam allowances. I found out it was so easy! You just cut the slit as far that it's as wide as your serge stitches when you press it open.
By the way, this is the elbow slit - it's not horizontal as the petticoat's one. I made it vertical so that it could serve as the base for the arm lacing (slit).
I use this way to sew a corner. I mark the place where the edges will meet. Then I draw a perpendicular to the basting. I join the point where this line meets the edge with the corner.
This is what I get.
I sewed it exactly at the bias lines and cut the excess off.
This way you can get neat flat corners:-)
I drew the line for the decorative stitches. I sewed along the lower edge, along the slit, through the drawn V and back to the lower edge. I sew at the serging line to attach the lining pieces.