Smoothly wrap around outside to bottom of tray. Glue fabric edge in place. Cover all sides with remaining fabric strip as above. Finish corners by cutting away excess fabric and gluing flat. Make a covered bottom panel for tray.
Glue trim around bottom of tray.
Place tray in case. Cut divider from lightweight cardboard. Add width of tray to twice height then cut. Before folding, measure and mark fold lines with pencil. If you use mat board instead of cardboard, score it before folding.