I need creative ways to fill up a hole so my cat doesn’t go inside of it

Hi everyone!

I just moved to my new home and I need help. There is a hole at the bottom of the kitchen counter where my cat likes to hide in and I would like to block it with something that makes sense for a kitchen.

The hole shown in the picture is 3.5” long and 4.5” tall.

I thought about a kitchen matt but it’s not thick enough. Any ideas?