What you will need:
USBImager
A Ventoy-ready drive
A smaller drive to temporarily hold EasyOS
Some time.
This was done with windows, My setup is Ventoy on my 2nd internal 240G SSD.
Your setup may vary. What's important is that you have two drives: a big one for Ventoy and a smaller one to temporarily hold EasyOS.
Here's how I did it.
1) Using USBImager, I wrote the EasyOS img file to my 64 Gig Flashdrive.
If the flash drive does *NOT* boot on your system due to Secure Boot being enabled.
2) Boot up Ventoy and hit f4
3) Choose "find EFi64x" (or whatever it is) The EasyOS flash drive booted up and did its setup voodoo expanding the storage partition and whatever else.
UPDATE:
or ... Press F2 and look for the 7 meg partition. On my system, it is hd0.
dig down to bootEFI64 (or whatever it is)
4) Do 2 and 3 a few more times just to be sure it all works
You could stop right there if you want. You have an EasyOS that boots under Ventoy. It works, but let's keep going.
5) Back in Windows, Use UBSImager to write the the Flashdrive into an .img file.
Done! Rename it to EasyOS.img and put it onto my internal 240-gig Ventoy drive. The EasyOS file is 64 Gigs, but that's OK. It works just like the Flash drive did complete with the "save" icon and it's way faster.
If it *DOES Boot* natively
2) Boot the flash drive and let it do it's voodoo.
3) Back in Windows, Use UBSImager to write the the Flashdrive into an .img file.
Done! Rename it to EasyOS.img and put it onto my internal 240-gig Ventoy drive. The EasyOS file is 64 Gigs, but that's OK. It works just like the Flash drive did complete with the "save" icon and it's way faster.
The only important part is having a flash drive the size that you want the finished EasyOS img file to be.
TLDR:
Write the EasyOS img file to a 2nd flash drive.
Boot the Flashdrive in some way and let it do it's setup voodoo.
Write the entire EasyOS flash drive into an img file and put that img file into Ventoy.
Updated for clarity. 25/Oct/2023