Model originally uploaded to Thingiverse at https://www.thingiverse.com/thing:5714430.

This is a way to use the controller board from a shucked 3.5" WD Easystore drive to make an external USB3 case for a 2.5" drive. There are two different bottoms, one for 9mm thick drives and one for 7mm thick drives. The two halves snap together so it doesn't require any fasteners.

I had to file off a little of the corner of the board so it would fit with the rounded corners of the case without needing to increase the size. 

I printed it in clear filament because I thought it would look nice and to see the LED. You could print in an opaque filament and drill a small hole for the LED.

Suggested print settings: 0.28mm layer height, 0.6mm line width, no infill, no support.