I designed this quite a long time ago to accommodate a AHB7004T-LM-V3 NVR board and a 2.5" HDD. Please ignore the bad quality of the prints in the photos, the printer was ancient.

The board is mounted to the enclosure with 4 3.5" hdd screws. The top cover has a place for a 2.5" HDD which is secured by a lip on the print on one side and 2 standard screws for 2.5" drives.

On the bottom there is a slot for a 75mm VESA bracket so you can mount the NVR to the back of a monitor, I do not remember if the slot design worked.

On the backplate there is a hole for a small KCD11 switch (https://s.click.aliexpress.com/e/_c3VFpPvN).