My sister told me today that a few people asked about her purple dress over on her blog. There are a few pictures in her post about our last event, Remembrance Day. I will include a few here just for clarification :)
Basically, she made the dress with my help and a friends. The skirt has four panels and is gauged to piping and the gathered bodice. We use the instructions from Elizabeth Stewart Clark's Dressmaker's Guide I think the question was more specifically about the sleeves though.
So, using the Dressmaker's Guide on slim sleeves (I can't say exactly how those are made because of copyright reasons so just use a close fitting sleeve pattern), I drafted those up as usual as a base. Once I had those cut out I started on the rectangle that is attached to the slim sleeve and gathered at the elbow and armscye. This sleeve is not for warm weather so keep that in mind :) So cut out your rectangle. The size doesn't matter that much as long as it is wider than your slim sleeve at the elbow and armscye and as long as you would like it. I do recommend cutting these pieces on the bias as the slim sleeve will be easier to wear and the rectangle on top will drape better. Now, all I did was gather the top and bottom edge of the rectangle and lay the rectangle right sides together on top of the slim sleeve. Lay it so that the bottom of the rectangle is where you want it to be attached near the elbow. You might have to measure a bit. Now sew straight across below the gathering stitches, flip it up and baste the top of the rectangle to to the top of the slim sleeve. Turn the complete sleeve right sides together to sew the under arm seam. Hem the cuff edge and then you set it like you would any other sleeve. I hope this helps some! Let me know if you all have any more questions or if I can make this clearer :)