Since the original posters pix are gone, here are mine.
I made a tray using the instructions and the attached pix are what mine look like.
One shot is edge on, so you can see how it is folded, the other is looking down on the tray.
I made mine using manila file folders for the base material, since I have a lot of it.
I folded the top piece, then lined it with velvet, using 2-sided tape to hold it down, then used 2-side tape to secure it to the bottom piece.
My first version used a valley 3/4 inch wide, figuring that the velvet would take up space. As it turned out, 3/4 inch was too wide, even lined with velvet. So I made the next version 1/2 inch wide, as per the original instructions, and it turned out just fine, for my pens, which are mostly slimline pens.
For the upper layer of a pen box, I taped the tray to a couple pieces of paint stir sticks (from Ace Hardware or Home Depot). The paint stir sticks provided the stiffness so it would not sag. And rest the end of the paint sticks on a couple more paint stir sticks cut to an appropriate height to clear the pens in the lower tray.