I can second the Zimaboard. I’ve got two HDDs hooked up to the SATA ports, and grabbed a cheap PCIE SATA daughter card for the SSDs.

I also used a PC power supply to run 12v to the board, and i use the built in SATA power cables. Look up “how to use pc psu as power supply”, it’ll tell you how to get it running without a motherboard.

Here’s my setup: PC case network setup