My usual method of attaching a collar to a shirt was to sew end to end and then backstitch. This has been hard to do on heavier fabrics because the ends are the bulkiest part.

Lately I have been starting in the centre back and working forward, it works better for me and now I do it on all shirts.

The ends can also be knotted and sewn in instead of backstitching, it should give a neater finish and be easier on bulky fabrics, I’ll try it on the next shirt.