The .3mf file includes the bottom and the cover, print them separately with 0.3mm layer height and no supports. The HDD and the Ewent EW7019 adapter should be quite a snap fit into the case, but you can use M3 screws to mount the hard disk and the cover too.
Feel free to use the included Fusion360 and STEP files to customize your enclosure, and share them here.
The author marked this model as their own original creation.