You will need
16mm FOE Elastic and the following lengths depending on your size.
1. NB-4mths 12″-30cm
2. 4mts-12mths 15″-38cm
3. 12mths-3yrs 16″-40cm
4. 3yrs to adult 18″-46cm
Cut your fold over elastic to length and heat seal your ends with a lighter or candle.
Overlap your ends about 1cm and sew together you can machine or hand sew.
I machine sew with a zig zag stitch.
Take a small lenght of FOE elastic to make a interchangable headband. Seal the ends. Put a dab of hot glue on the back of the headband and glue the sealed end.
You now have a interchangable headband. You can add a fabric flower, or ribbon hair bow.