We start of by taking the front piece and back piece of the pattern you are using to make the garment. Put them with the neckline together but the shoulders slightly overlapping (perhaps by 0,4 inches / 1 cm ) And copy 4 inches (10 cm) of the center front and centre back. Also copy the whole neckline.
Lower the centerefront by 0,4 inches (1 cm)
Mark out the width of the collar, the same all the way.
Fix the shape of the front, if you are bad at making round shapes, use a small bowl or a glass or something, that is what I do,
Now we will reduce the length of the outer part of the collar. Make triangles that are about 0,2 to 0,4 inches (0,5-1 cm) in the bottom and goes to the neckline.
Cut out those triangles.
Tape it together, now you are finished with you pattern.
The amount you take of the outer part of the collar decides how high they get. To the left is a collar with a lot taken out and to the right is a collar with not so much taken out.