Just a quick project I threw together when I was bored one day.  I saw something similar while browsing 3D print designs on Pinterest one day and decided to try designing something similar just from memory.  A wrist rest for use with a computer mouse.

Depending on what type of 3D printing technology one uses for this, I assume you can get different amounts of flexibility from the finished product (say FDM printing vs SLA printing).  Changing the size and configuration of the pockets would also change flexibility; this would be a good thing to parameterize for different test prints.