Youtube, but hand stitching should give neater results (apart from for top stitching maybe). You also have a lot more options available when hand stitching than on a machine.
This is a good book to learn better hand sewing
https://www.amazon.co.uk/Couture-Sewing-Techniques-Revised-Updated/dp/1600853358
Sarah's dress fits that way, because it is an extremely structured dress. It is heavily boned, and likely she's wearing an additional structured garment underneath it that sleeve stays are tucked into. If you can't let the dress out enough to add boning and a waist stay, your other option would be an underbust stay--or attaching a strapless bra-- you would anchor a piece of elastic in the middle of your underbust, through basically belt loops all the way around your underbust, and add a hook and eye closure to the back. From there you can add small rods of boning to the under arm to tuck into your undergarment to keep them in place or adding basically a harness of ribbon or elastic across the back from the end point of the sleeve ending at the opposite side waist/hip seam, on both sides.
You might find Couture Sewing Techniques by Claire B. Shaeffer to be very helpful. She has detailed instructions on how to add all kinds of shape-perfecting stays.
Did you happen to read about it in "Couture Sewing Techniques" by Claire Schaeffer? It had great tips for shrinking wool plaid or patterned fabric, so that there wasn't any interruption of the design. That's where I got the idea to steam-shrink wool in both knitted and sewn clothing.
I have the older edition of this book, but it's an amazing resource nonetheless:
https://www.amazon.com/dp/1600853358/ref=cm_sw_r_cp_apan_glt_fabc_2D8E2M36AX9B7XHSAJ6V
Claire Schaeffer's book Couture Sewing Techniques is an excellent resource for all kinds of hand sewing techniques.
The book has drawings instead of pictures for the techniques, which is not as desirable but still the explanations and tips she gives for every technique are extremely valuable.
However she does have some great pictures of some beautiful couture garments as well as the insides of garments which is great.
And for the amount of information in the book, the price is remarkable.
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Couture Sewing by Claire Shaeffer. She also has more specialized books on the parts of Chanel-style suit, such as The Couture Cardigan Jacket and The Couture Skirt. Here's her Amazon page.
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Thomas Von Nordheim's Vintage Couture Tailoring is excellent. He did the structured costumes for The Phantom Thread.
I've only looked through it, but Zoya Nudelman's The Art of Couture Sewing had beautiful photos.
Roberta Carr's Couture: The Art of Fine Sewing has hideous examples but good information.
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For pattern making, Helen Joseph Armstrong's book is very popular. Books by Ernestine Kopp and Natalie Bray are others.
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That is an excellent plan! Meanwhile, you can work on your sewing skills. You may need help with fitting your dress, nice it is close fitting garment. Craftsy has some excellent sewing classes. Get on their mailing lists and you will receive offers for a membership for $2.99 or there about for your first year. Craftsy has video classes on sewing, knitting,crochet, cooking….lots of subjects. I like to recommend as a sewing guide Reader’s Digest Guide to Sewing as an excellent book to learn how to sew or learn different technical techniques. You can usually find a used copy very inexpensively. Threads Magazine also published books on formalwear sewing. I used to be a custom gown designer and used a lot of their books. Susan Khalje published an excellent book on sewing eveningwear. She also has a sewing class on Craftsy.
Couture Art of Fine Sewing and other sewing books by Taunton Press are excellent.
Reader’s Digest Guide to Sewing 2010 ed
Readers Digest Guide to Sewing 1981 There are used copies starting at $10.99 Don’t let the age of some of these books throw you off, the sewing techniques have not changed very much over the years!
I also like the website Pattern Review for sewing machine information.
On a related note, I have a really excellent book on couture fashion that I'd recommend you know more about this https://www.amazon.co.uk/dp/1600853358/ref=cm_sw_r_cp_apa_2cwaCbDSE1186
I don't have a workspace, I just use the floor, but I can give you some book ideas. I've recently been really into learning about Haute Couture and Claire Shaeffer's books have been very helpful. I find her books super informative and easy to read, and I can easily see myself applying many of her techniques to every day sewing. The books I've enjoyed so far are Couture Sewing Techniques and Claire Shaeffer's Fabric Sewing Guide. I really want a hard copy of the latter as it's a fantastic reference, I have the kindle edition right now. She also has another fabric guide book that is much less detailed that is handy too. Another good book is Vogue Sewing which was one of my first sewing books and is a very useful reference for anyone, especially if you're following a pattern with unfamiliar techniques.
Also, don't be intimidated by the word couture. I know people generally associate it with super fancy difficult sewing, but Claire Shaeffer breaks down the techniques really nicely and I feel like I have a better understanding of how sewing works on a general level now. It's not scary and I'll definitely be using many of the techniques on my next project!
http://www.foundationsrevealed.com/index-of-articles/free/advanced/277-supporting-a-large-bust
http://www.blogforbettersewing.com/2011/05/net-corselet.html
http://chainstitcher.blogspot.com/2013/02/ever-wanted-to-see-inside-1960s-dior.html
In general, boning helps distribute the vertical tension (keeping things from buckling and wrinkling), but the fabric does the work of shaping. You might consider using double boning (two bones in side-by-side channels) along the existing pattern marks, extra single bones in-between, and steel bones instead of the plastic typically called for in garment patterns (probably spiral steels for flexibility). That said, if you've never done corsetry before...I won't say don't, but do at least give yourself enough time to do a mockup. The things I linked to are couture finishing techniques, and for a reason.
A strapless bra is very often worn with this sort of dress for the busty among us, possibly with a long-line bra or bustier (even with a built in waist stay, corselette/torsolette/bodice). As far as I know, the dress usually isn't attached to the bra in any way - as long as they're both fitted correctly it shouldn't theoretically be a problem. A super well fitted integrated corsetry piece could substitute for the bra, and I've seen it done very well, but IMO this is a bit advanced work. It also doesn't provide quite the same shape as a bra.
I think in general, especially for your average non-couture level strapless dress, it's a war between the dress and the boobs (very often in a strapless bra that's not tight enough in the band to keep it staying put).
If you want to read some more about this, try Couture Sewing Techniques by Claire Shaeffer. You can read a bit of the relevant info on google books preview