The internal SSD
is formatted GUID, single partition, Mac OS X, journaled.
Nothing special in BIOS settings. I have bluetooth enabled and legacy USB is currently disabled but you need to enable that to boot from USB. Disable it later. I don't think I changed the boot order, just make sure it looks sane. If you press 0 when you see the DELL boot logo you should be able to select the boot device you want. The Mini will go through the list and boot from the first thing that looks like an OS. So after you clone the drive, unplug the USB and it should just boot from the SSD
I believe there's a boot loader installed by DellEFI 1.2a5. You see one when you boot. There is nothing connected to the Mini9 to get it to boot the first time, of course you will probably still have the USB drive you cloned from plugged it.
I used the default settings when I ran DellEFI 1.2a5, I think thats everything that doesn't say "not recommended",
You need to use software that will make a bootable copy when you clone the external drive to the SSD
(called blessing the drive). CCC will do that if you choose the right options. I haven't used CCC for 5 or 6 years, so I can't tell you what they are. SuperDuper! is a little more intuitive to use but it's less of a swiss army knife and you need to pay for it. Either will work, just read the docs carefully.
Read some of the How-To Guides to get a feel for what that first boot is like. Keep an open mind, you're not going to exactly follow any of the guides, but you will encounter some of the same situations. The idea for installing to a USB disk drive then booting the Mini9 from it and cloning it to the SSD
came from How-To "load directly to a RunCore from a Mac".