So you've made a mock-up of your corset pattern, changed it based on how that fits, and made another mock-up. You like how it fits. You have your final pattern. You have your materials. You're ready to make the damn thing already!
WAIT. First you have to decide what construction technique you will use. The method you choose will depend on your skill and comfort level, personal preference, and desired appearance or use of your final corset. There are a bunch of different methods of constructing a corset, but most of them are sort of advanced. I think there are three main construction methods that you need to choose from as a beginner.
1. The Sandwich Method - This is the most basic method, really. It's the one that most beginner corset patterns use, I think. The idea here is that you have two layers of strength fabric, and you sandwich the bones in between these two layers. Each layer is put together on it's own, then you match the seams up and sew the layers together to make the channels for the boning.
Sidney Eileen has a great tutorial for making a basic two-layer corset. (The rest of her tutorials are excellent as well. I will refer to them again.) Keep in mind that you can use the two-layer method even if your corset has more than two layers of fabric. I usually cut my pieces of fashion fabric and strength fabric and I flat-line them together. This means I put the fashion fabric onto the strength fabric and sew all around the edge to attach them. You can also attach them using fusible web. This can give your corset a really smooth look, but different brands of fusible web work differently, so test it first. So you have an outside "layer" that is really two layers of fabric. You can have your second strength layer either double as your lining, you can attach it to a lining layer in the same way as the fashion layer, or you can add a floating lining that is only attached at the back and front of the corset, but doesn't have all the boning channels sewn through it. (More on that later.)
Advantages of the sandwich method: It's fairly easy to understand, your boning channels are relatively smooth and thin, you can place the channels anywhere you want, and since you assemble the whole corset in layers before putting in any boning, you can try it on or at least hold it up to you to double-check the fit before putting in any boning. I used this method for my most recent corset because I wasn't 100% sure of the fit of the pattern I was using (do as I say, not as I do) and I had to rip it apart and reassemble it a bunch of times.
Disadvantages of the sandwich method: This method require very precise sewing, since if you vary your seam width at all, the seams will not match up perfectly between your layers and you will get bunching or wrinkling in these areas. I'm not a very precise sewer, so I don't like this method. My last corset had a couple of places where the lining layer was smaller than the outer layer and the outer layer bunches in those spots. Ick.
2. External (or internal) Bone Casings - This method is also a pretty simple idea. You have your corset, which is fully assembled without any boning. Then you make little tubes of material to hold your bones and you sew these casings down on the outside of your corset. This can be a very striking style, and it's one I really like the look of. Check out this lovely example:
To make the channels you will take strips of your strength fabric and strips of your fashion fabric and sew these (together) into a tube that is just larger than your boning. It may take some experimenting to figure out the right width of strip to use. You don't need to sew the tubes with right sides together and turn (that would be a pain!) Just sew the edges together and when you lay the tube down on the corset the raw edges will be hidden behind the casing. Before you sew your casing onto your corset, you want to press them into shape, but you need to use a quilter's pressing bar inside the tube. This makes the casing conform to the right shape to hold the bone. Then edge-stitch the tube down on both sides and insert your bone. You can also put casings on the inside of the corset (usually covered by lining) using the same method. This is a more secure and heavy-duty option.
If I ever do another externally boned corset, I'll make a full tutorial. Right now that's not on the horizon, though. I haven't found a real tutorial of the method I described above, but I found this video on how to use pressing bars to make internal and external casings. The second half is what I've been talking about. I've never considered using the bars inside the fabric while stitching, though. That's a great idea.
Advantages of the External Bone Casing Method: It looks damn cool. Also you can make a really thin corset with just one layer of strength fabric (good for summer!).
Disadvantages of the External Bone Casing Method: It can be time consuming to make all the little casings. Also, my only corset made this way is my everyday corset that I wear to sew in, and after six months the bones have started to wear through the casings, because on the front of the bone there is only one layer of fabric holding them in. Also, the external casings stick out a lot more than internal boning does, and that wouldn't be ideal for something you want to wear under clothing without showing.
3. My Favorite Method - Ok, I don't think this method has actually got a real name among corsetmakers. I've seen it called the welt-seam method, the flat-felled seam method, and just the volutelady method, after the person who first posted about it on the corsetmakers community on livejournal. I'll call it the Folded Seam Method cause it needs a descriptive name, dammit. (Ooo, we can call it the FSM, and then it will be confused for the Flying Spaghetti Monster!)
The idea with this method is that you construct all layers of the corset at once, panel by panel, building the boning channels into the seams as you go. Here, there are diagrams here. This is my preferred method of corset construction and I am going to do a whole photo-heavy tutorial on this. Here's a picture of a seam done in this method, with a bone inserted.
Advantages of the Folded Seam Method: It doesn't require the same precision as the sandwich method. You are putting all the layers together at once, so they are always the same size. It's also very fast. You just sew your seams once, instead of doing it over and over for each method and then stitching some more for the boning. Three lines of stitching for each seam and your bone is placed and you're done. It's also very secure, since the bone is sandwiched between the seam allowances of ALL the layers of your corset. That puppy ain't coming out anytime soon.
Disadvantages of the Folded Seam Method: The seams/boning channels can get bulky with all that fabric in there, but I don't think it's unattractive. You only make the corset once, so going back to make changes is pretty much impossible.
So, I hope that wasn't too confusing. Tomorrow I will start working on my tutorial for the Folded Seam Method. It will take you step-by-step through making a corset with one layer of strength fabric, one layer of fashion fabric, and a floating lining. In the meantime, I'm open to answer any questions.