A good way to display fixed blade knives is to fasten some powerful magnetic strips to a plywood back and cover the lot with felt. The magnetic strips being raised a bit so the knife hilts will clear the backing and the blade can adhere magnetically to the strip.
If you desire a glass front, just build up the sides and use a picture frame hinged to the box as a door.
Makes a very nice wall display case and the knives are very easy to arrange and get out of the case for use.