So this is where I've completely given up on the pattern and am just winging it.
1. First of all, pop your dressing gown on, on a mannequin or on a hanger and have a look at it. Does it look like there's a nice gradient from the front to lower in the back?
2. Use a tape measure to measure from the edge to the floor for the ruffle and remember to add a bit for seam allowance. I did my ruffle at 15" height, but remember, I'm short! You may well need longer. Ideally you want it just on the floor at the front so it has that insane decadence, and you have a train effect at the back.
3. Measure around the long, long, long edge of your gown. Mine was 228" wow!
4. Decide how much extra volume you want in your ruffle (and check how much fabric you have left!) I went with double my edge so 456" by 15". Remember if you are adding marabou or trim, you are going to need this length of marabou/trim too!
5. You'll likely need to add pieces to make the ruffle. I did two lengths of 228" plus a bit for seam allowance and made a centre back seam. To do so with a French seam, wrong sides together, pin, sew 3/8", press, trim, flip and sew 1/4", and press to one side.
6. Finish the short edges of the ruffle as we have done previously with a straight stitch at 3/8", trim and then zig zag over, press. As I was adding marabou, and as tulle does not fray, I left the massive long edge of my ruffle raw.
7. The run a gathering stitch, allllll the way around the ruffle. Due ot the volume, I actually did this in two parts to the centre back seam. Due to the fact that tulle is easy to gather and the volume of fabric, I just used a single gathering stitch, unlike the two I normally use. Just be wary not to pull too hard and snap it when gathering!!
8. Now in an act of complete and utter lunacy, I decided to do a French seam here. It was mental, I don't advice it, it was hell to do. But it does look pretty.
9. Mark the centre back of the gown and pin the middle seam of your ruffle.
10. Pin the edges of the ruffle to the gown.
11. Now gather evenly like a crazy person! You may find it's useful to half and even quarter each section so your gathering is even. Pin, pin, pin!
12. Sew and press your seam (whatever seam treatment you are using). 13. Dance around in your frou frou gown.