Where a hat is shown being worn it would appear to be a simple conical shape. The Tollund man wore a pointed leather cap fastened under his chin by thongs. These instructions show you how make a similar cap.

• Divide your head circumference (Q) by four.
• Make four rectangular panels this wide plus a little bit.
• Divide your ear to ear measurment (Z) in half.
• Each panel needs to be at least this long.
• Depending on how deep your head is - shape the panels into triangles about halfway up.

• Stitch the four hat sections together along the crooked edges.

   I would recommend hand-sewing the hat as you may not want to wear it all the time and you don't want any machined seams to be visible, do you?   
   To hem my garments I fold the edge over about half a cm and then again about another half cm and stitch down with a running stitch. For my hems on wool I use a wool thread. You can use thread the same colour as the hat or a different colour - to tart it up a bit - and you can add tablet-weave along the edge as well.
    For leather or sheepskin, the hat should be fine left as it is.