I cut the collar on the bias in one piece- without a CB seam because of the bulk (and extra work) a seam would add. You would usually have a CB seam in a bias cut collar - such as the under collar on a suit -because you can ensure that the bias is the same on both halves. The 2 biases in a fabric stretch differently.
I check the collar one more time by pinning it to the neckline, then I bound the outside edge with bias binding and serged the neckline edge.This collar will only be one layer of fabric thick. This was only being worn a few times so a serged edge was ok.
I proceeded to hand stitch the collar to the neckline of the coat. I am using a heavy button/craft thread to do this and whipping evenly over the serged edge
All done- here's the finished collar installed and the coat is now ready for trimming which I will show you next. You will notice that with the one piece bias collar, the quilting pattern is not the same on the right and left, since I was covering the collar with "fur" it did not matter. If it didn't get trim it would have been a better choice to put a seam in the CB and have a symmetrical look.