Here is the shirt card I made for Father's Day. This is a mini card but you can enlarge it to meet your needs as long as the same amount is added to each measurement. You may want to be more careful to fold your collar evenly as I did this quick and as you can see, it is not even but I am sure you get the ideal.
The center would be 2 1/4" (on the 4 1/2" side) so gate fold to that point. Then turn the top back about 1/4" or so and fold (This will become your collar).
My only suggestion is to do a few small ones for practice. Get use to the folding and how it works then have fun. If you have any questions or something don't make sense to you feel free to shoot me an email. Have a wonderful Memorial Day (and don't forget the reason for it).