Method 1: This is the method that I used although I don't recommend it as method two seems much easier. Essentially what you will do is take measurements of your entire face and neck and then continuously fit it to your face until you get it to fit right.
The measurements I took were:
Ear to jaw, jaw to chin, over my mouth from my jaw, over my nose from under my ears (picture 1 of the first picture), and bridge of my nose to chin (4th picture on the first picture). For the neck they were chin to collarbone (3rd picture on the first picture) and the area around (2nd picture on the first one).
I would then hold it up to my face/neck and trim it/add paper until it fit then transferred it over to Craft foam and did the same thing since it had a stiffness closer to that of the fabric I chose to get the closest fit I could. I redrafted the neck many times until the curve was right. The mouth was mostly guess work as well (I would recommend practicing drawing the shape a few times until you're satisfied with how it looks).
Once I was happy with the pattern I transferred the final draft back onto paper and added a 3/8 inch seam allowance to all edges.
The eye patch is much easier to do. You pretty much just cut out a rectangle that can cover your eye and add two straps to the sides. I sloped the sides so that they would avoid my ear and other eye.
Method 2: This is my preferred method of drafting patterns, but I didn't have any painters tape at the time. What you would do is wrap your face and neck in cling wrap over any part the mask would cover (leaving holes so you can still breath) and cover that in painters tape. Get a friend to help if you can. Then you would cut yourself out and draw out the seams so that you can recreate it out of fabric. You would then transfer it over to paper and use that for the next few steps. If that doesn't make much sense then here's a video from Kamui cosplay explaining the method better: