Choose a fabric that pleases you - white is most commonly used, but have fun mixing and matching. Cut a strip 4cm longer than your collar length measurement, and 2cm wider than your finished width measurement. I cut mine 70cm long and 16cm wide - a bit shorter and wider than I should have due to fabric constraints.

Note: If you have a pre-made han eri, you don't need to cut it. However, do follow the directions below. Store-bought han eri are usually longer than 70cm.

Fold in the raw edges lengthwise and iron. Check to make sure the final width is the same as your measurement (see photo above). Fold over and iron the ends, then fold the entire han eri in half and iron. It should look like this now: