Stack Exchange network consists of 175 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.
I want to make these 2 inner faces with rounded edges like the left image
At the right image I used Ctrl+B to make the outer edges of this board rounded but I can't apply this to inner face as the board itself is a cube with some modification
For your example this could do the job:
Required, but never shown