What I have been doing for my custom pen boxes is this. I cut a piece of mdf to fit inside the bottom of the box. I measure out evenly spaced lines for the number of pens I can fit into the box. Using a core box bit in my router table, I cut the chanels needed in the mdf. There are four different ways I will finish this tray. 1- Sand and stain or paint. 2- guild in gold, silver foil, or some other material. 3- Cover the tray in self stick felt or fancy Japenese paper papers. 4-Use my flocking kit to add any color felt I want to line the case with. I added several photos of boxes I have finished in this manner. I am sure others have their own ideas and methods. Very nice case by the way. Jim S