Don, I have bought a yard of velvet at the fabric store, and then cut some thin cardboard the size of the inside of the box and wrapped the velvet tight to the card board and put a little glue on the back and fit it into the box.
On silverware cases, I have put glue on the wood with the slots for the utensils then laid the velvet on and pressed it down into the slots,and formed the sides by hand.
Herb