Progress on Winter Dress

Working on my Winter Dress Project and now stuck and in need of help! Started last week by cutting all my fabric pieces but couldn't start sewing as I ran out of black thread. Placed an order online and I'm now stocked so started sewing yesterday. Was very anxious as it's my first time sewing with corduroy but have to say it hasn't been bad. I had to zig zag all the raw edges because corduroy ravels like crazy. It also sheds some "fluff" which is now everywhere. I decided on some design changes. My initial though was to insert sleeves, after all it's a winter dress. But when I gave it a bit more thought I realised it wouldn't make a difference as even with sleeves the dress wouldn't be warm enough for me to wear in winter. So I decided to do the sleeveless version and use it with a nice close fitting jumper underneath. Because I want to keep it simple I'm not doing the collar either. The princess seams were fairly easy to sew. They are a bit of a nightmare but with care and attention it works out fine. I also had to chop off 11 inches from bottom as it looked like I was out of the Little House on the Prairie 80s TV series.  This is what I have so far:

I've constructed most of the dress, attached the lining, finished neck seams and have the back seam and invisible zipper to do plus finish the lining in the armholes. And this is where I'm truly stuck and in dire need of help. I have found several tutorials on how to attach lining to sleeveless armholes but a) they are all in fabrics less bulky than corduroy and b) all have the side seams still open. I have thought of a way to do it but would love to finish it the right way, if that makes sense. Below are Sew Magazine instructions for the armholes and it's gibberish to me. I have read it countless times and have not yet made sense of it. I am sure it means something very simple and once I crack it I'll be like...duhhh!! But for now I'm truly stuck, so if someone knows about this or can make sense of the below please leave a comment or email me at : suzysewingblog[at]yahoo[dot]co[dot]uk. Thank you!