Separate collars and cuffs were developed (read the history) in the late 1800s by a beleaguered housewife who didn't like having to deal with the "ring-around-the-collar" of her husband's shirt. They were used extensively throughout the Victorian era and persisted until just after WWI.
So, I got out my books and my drafting tools -- protractor, French curve, rule, and a pencil, as well as looking things up on the Internet.
First, I made a paper mockup of how I thought I wanted the collar to look on my costume. When I had an approximation of the correct angles, I started to draft.
The Burda website (link below) was probably the most useful on how to draft a collar, and walks you through creating a collar stand and actual collar using the measurements for your shirt.
I had to make several different versions of the collar with various "angles" to see which one would actually lay correctly on the costume. The steeper the angle, the more the points of the collar flare out (think 1970's collars), so I went with a fairly sedate angle of 7 degrees.
Tip 1: One of the keys to getting a really nice crisp edges and points is to make sure to press it well, which can be hard, but this tailor board really helps in pressing those hard-to-reach places.
For example, using the "tip" of the tailor board, I can effectively press the fabric down. so that points are easily pressed.
Tip 3: Use a point turner to help turn the points and to press the seams.
You eventually get a nicely turned collar.
For this cosplay, the collar didn't need to be super stiff so I used only a light interfacing on the collar. The rest of the stiffness comes from the linen.
Then it was onto the cuffs, which required a similar, but different design. This piece was a bit harder, as I couldn't find a lot of information. At first, I tried to actually make the cuffs just like the collar (in two separate pieces), but the mockups didn't look right. The cuffs shouldn't have that middle seam.
After ruminating on it for a day or two, I turned to costume.org for the book, The Cutter's Practical Guide 1893-1898 by W. D. F. Vincent, which had some good illustrations of the various types of cuff and collars, which was extremely helpful! (Cuffs are the bottom 3 illustrations).
I took the cuff pattern pieces I made, which was close to how I wanted it to look, and combined the two of them, aligning them at the bottom seam allowance.
Here are the mocks (from bottom to top), the collar, the first attempt at the cuff, to the final version of the cuff.
The final mockup looked pretty darn good, so I made the final ones in my linen.
Normally, cuffs and collars are buttoned into the piece of clothing and have button holes created for them. However, I decided to not use that function, but instead opted to carefully tack down the collar and cuffs for a slightly permanent fixture so that I wouldn't have any wardrobe malfunctions on stage.
More on this cosplay at a later date.