How do I go about making that spare exactly like the one I create songs AND gig with?

Take MOXF #1 (the one with the Flash Board in it).
Make a MOXF ALL data File with Samples.

Press [FILE]
Press [F2] SAVE
Set the TYPE = All
Give the File an Name
Mark the box "with Sample"
Press [SF1] EXEC to execute

When you want to create the clone... power down MOXF #1, remove the FLASH Board
Plug it in MOXF #2... power it ON
Move the USB stick with your ALL data to the MOXF #2
LOAD the File
Press [FILE]
Press [F3] LOAD
Set the TYPE = All
Mark the boxes "with Waveform" and "with System"
You can leave the box "with Sample" empty - the Samples are already on the FLASH BOARD

Once you have loaded the FILE with Waveform and System... these will remain in the MOXF #2 until you make an effort to remove them...

As long as the WAVEFORM List is in your MOXF #2, you will not have to ever load them again...
You can review the WAVEFORM list at any time by going to [FILE] > press {F6] FLASH > Press [SF2] DELETE

Here you will see a listing of the current Waveforms in memory... (obviously, you can DELETE items from this screen, but you simply want to review the list... there can be 2,048 Waveforms on the list maximum.

This is the list of information that tells the MOXF *where* to look on your FLASH Board to find the audio samples.

From the article on MOXF Flash Boards.........

How it works:
If you load an All data file, a library that does not contain sample data, you will naturally overwrite the Voices in the internal USER 1, 2, and 3. This does not, however, affect your Waveforms, nor your Samples. If you later want to reload your "MainSet" back in...
........ Your Waveforms and Samples are all there, already........

Your Samples are already on the Flash Board. So you don't have to wait 20-40 minutes it would take to re-INSTALL your data. Simple pop the Board into the new MOXF... Load up the Voices
Load your "MainSet" "with Waveform" but clear the box that says "with Samples".

Extra Credit:
Link -- MOXF Flash Board

Thanks, Bad Mister.

So I'm clear:

-- The Flash Memory is simply swapped and re-introduced into MOXF #2.

-- The ALL SAVE and ALL LOAD process (minding the Waveform and Sample box "rules") takes care of the Voices/User Banks/Slot Assignments where the aftermarket (non-sample) Voice Libraries reside. (Cause reconstructing voices and assignments would be a major and not very straightforward chore.)

-- The steps you describe above, technically, turn the MOXF #2 into the Main Keyboard, by virtue of it now having the Flash Board as well as all the User Banks verbatim.

Question: Should I use an extra large thumb drive for the "cloning" process or is it not really that much data being moved, stored and re-loaded?

Question: Will my Utility and other "personalized" settings be lost or require re-doing the settings?

Question: Will my back-up User Arp, User Voice files, etc. need to be accessed?

Thanks for your patience. Every time I get a new keyboard I stress out, remembering what and how long it took for the current keyboard to evolve into it's present state since I've long-since forgotten how it got that way. Because of the humidity and salty air in Central America, I know in a very short amount of time the elements will take their toll, so having a back-up or two all ready to go seems like a reasonable precaution.

OK. So I'm adding a twist to my request about making my spare a "clone". I went ahead and purchased the FLM board BUT it's the 512g version NOT the 1000g. I checked the available volume on the main keyboard memory and it appears I have not used but half of it. So I figured it would be safe to get the smaller board. Wrong?

So, the scenario of having to remove the memory board and put it into the spare is now moot. My goal, again, is to be able to grab either keyboard, plus my thumbdrive and walk out the door if necessary.

I presume there are some steps in the thread above by BM that could be different now. Again, my goal is simply to have the two keyboards be essentially clones.

Would it make sense to go into the larger memory and delete some wave forms and samples I don't use so I don't max out the 512g. How WOULD I go about deleting things on a memory board without creating problems for myself? I'm thinking the Melas software might offer some options.

You're going to be installing the sample data onto the new 512MB Flash board using your original purchased expansions.