Dell Inspiron 620 Issue - SATA HDD Not Detected In macOS

[Injury]

One way and probably the easiest is to copy the EFI folder of your USB installer drive to the desktop, now mount the EFI partition of your hard drive, find and delete the EFI folder that is currently on the hard drive and replace it with the one you copied from the USB drive.

That should make the HDD appear in Disk Utility?

 

[Injury]

What flags/settings did you use to get into sierra?
I've tried everything but all I end up with is a row of +++++++++++++++ followed by a reboot.

Are you talking about booting into the UniBeast installer USB or the OS drive?