Basically mukluks are a skin boot.

• Some people substitute velvet for the main part of the boot and line it with quilted fiberfill. 
• The bottom is made of skin, you could use sueded leather, something that wouldn't slip on the ice.
• The top is decorated with beads.  You could use rickrack for this.
• Then the top has a drawstring to pull it tight around your leg.

The boot usually goes up to just below your knee.  You could buy a felt boot liner and make a cover around it, and it would look just like mukluks.

Mukluks are only worn when the temperature is cold.  The boots do not repel water very well.

I've drawn a picture of a pair of mukluks for my post cards page.  I've drawn it made with seal fur and wolf fur around the top.  Click on the thumbnail photo for a larger view.