This is a multimaterial project combining 3D printing with basic wood cutting.
You will need a piece of 18mm (3/4") Plywood cut to 149mm (5 13/16") front to back in order to fit into the holes. The ends have a 3mm cap (1/8") to close off the side and prevent them from sliding towards the middle of the stand.
Measure and cut your board to the desired length. I had 769mm (30.25") to fill so I cut mine to 762mm (30") and had barely enough room to fit into the cabinet.
Print in PLA or desired material. The middle support is not required but will help prevent sagging over time. Print 2 of the end pieces to complete the project.