The Asrock N100DC-ITX uses a 19v power brick so no separate PSU to power the drives. It comes with a 4 pin cable that splits into 2 SATA power.
The case I chose, Silverstone SG13, comes with a 3.5" HDD bracket but you need to mount the drive belly up so you can screw it in. The second drive I want to put where the PCIe slot is, found a nice 3d model for that. The thing is, the power cable would be too short and the drives would be too far apart to reach both.
So I removed the HDD bracket and cut 2 L-shaped aluminum stripes and I screwed the drive belly down. This way the cable now reaches both drives. I know, I could have cut the cable and made it longer but I prefer to avoid playing with power cables if I can.
Turned out quite good. Wanted to share it with other people. Now I need to find someone to 3d print the PCIe HDD holder and find some rubber stuff to put under the L-shapes to dampen the sound of the drive. This is the 3d model, https://www.printables.com/model/385403-pci-slot-hdd-bracket but V2 with the nice feet.
PS the drives in the images are broken so I just used them as dummy drives.
That's about it.
Huh. Kind of surprised it supports up to four drives, but if that's what it says, there you go. Shouldn't be any risk of drawing too much current through the wire. At most the board or PSU would shut down.
Also, if you are putting more drives in, see if the BIOS lets you enable staggered spin-up, so that they aren't all peaking at the same time.
Will do, thanks!