Just a quick cloak diagram and explanation. Eventually, I’d like to clean this up and create a real tutorial.
For 14th century cloaks, I recommend a half circle. Depending on length, no sewing may be necessary at all (except for the neck).
The extant cloak I rely on the most for construction information is the Bocksten Cloak.
There are a couple of examples of cloaks like this. They’re pieced along the length of the fabric, using the selvedges. One might consider cutting each piece in half or adding a false seam, depending on the class portrayed, although, it seems that wool broadcloth was generally available. Using the wool in narrower widths and piecing might result in a little less waste, although the full circle wastes less than I thought.
In the late 14th c. at least, men’s cloaks seem to be fastened on one shoulder, and women’s are fastened in the front. The shape of the neckhole changes slightly, but both should be shaped on the shoulders, so it stays on more easily.
As for fabric, use wool, the heavier the warmer! I wouldn’t suggest anything lighter than flannel, but melton or coatweight would be the warmest. I don’t recommend lining cloaks, unless you need it for decoration. If it’s wet outside, and the linen lining picks up any water, it’ll wick it up like nobody’s business. Also, if you have a heavy enough, fulled fabric, you might not even need to finish the edges. This can be a quick evening project.
Construction Diagrams:

Image 1: After constructing the half circle, either by just cutting or piecing, lay it out on a large, flat surface. Fold the sides down along the red lines, which will give you image 2.
Image 2: The cloak, after the sides have been folded down. Here is where you can control how much the cloak naturally hangs open. If you fold it so the edges don’t quite meet, it’ll hang slightly open, like some formal 14th century cloaks, and like I did on a friend’s Pelican cloak. If the edges meet, it should hang closed. I haven’t tried yet, but you could conceivably overlap the edges slightly to help it stay closed better, but I’d play with it before sewing or cutting much of anything.
Image 3: A closer zoom of the neck area. Sew (or rather, pin) along the red lines. This is the fitting around the shoulders that keeps it from slipping back or gaping around your neck. The length of the red lines is from just above the point of the shoulder to your neck. Don’t cut the shoulders yet. The angle depends on the slope of your shoulders – you usually want some sort of slope.
Image 4: Cut out the neckline. Cut the hole too small to start with – by the time it’s on the bias and you add a seam allowance, it’ll be bigger than you think. You can either cut a plain neck, or, as I’ve diagramed here, a little bit of shaping around the front. I think having the shaping is more comfortable. The cloak pins shut where the shaping comes together.
As a note, I drew diagram 4 after 3, because it’s easier to visualize sewing the shoulder slope before cutting the neck. Realistically, you’ll probably mark and pin the shoulder slope, and cut out a bit of the neck so that you can try it on to test more easily. Just don’t cut too much away that you might want later.
Feel free to comment, ask questions, etc!
ETA: Don’t cut the half circle shape until you’ve fit the shoulders, and can have it hemmed. The half circle will actually be slightly elongated to accomodate for the width of the shoulder.