At the beginning of December, when I still had my sewing machine working, I made two matching elf hats for my sons. I used a fleece blanket from Ikea and an old jersey T-Shirt for the inside of the hats. I find it very strange that you can buy 1,7m long fleece blankets for 3-4 euros but at the fabric store they cost 5-8 euros per meter.
For our (almost one year old!) baby boy I had to adjust the bottom, so we can close the hat under his chin with velcro instead of tying laces.
When the hats were finished, my older boy asked me to sew laces on because his ears were still cold in the hat. So I added those later.