These spreading board of insects are made with an additional coating of soft wood balsa (3-4 mm thick) or cork (3-4 mm thickness). The coating of the cork tree has 2 different fractions of a smaller and larger grain. You can determine the coating material from the photo.
At the bottom of the hole is a strip of cork or isolon for a soft fixation of the central pin

This set is a sample of shields that I can make for you under the individual order to the dimensions you need.

You can see all the dimensions of the good in the photos.