Backing up boot partition + main partition to external SSD to boot from it?

Hello, I managed to do this once before a long time ago but can’t seem to figure out how I did it.

My main SSD is dual-boot Windows 10 and Manjaro, where I use Manjaro for work.

A while back I somehow copied the boot partition + Manjaro partition to an external SSD. I can’t remember how I did that, but it works great. If I were to take out my internal SSD, I can boot to an old copy of my system with the external SSD.

I’m trying to do that again, but onto a new external SSD (and a much more recent copy of my work system).

Is there an easy way to go about this? The new external SSD is empty, with just an ext4 partition. I tried making a copy of the partitions using Clonezilla but it created image files instead of cloning the partitions / files so I don’t think I did it with Clonezilla.

Maybe I used Gparted? I’m not sure, my brain is currently not working.

Any help would be appreciated, I’m currently still researching trying to figure out how I did this.

dd or Clonezilla can theoretically work.

There’s an option to do disk to disk or partition to partition. You don’t have to make images.

I copied the EFI system partition and then the Manjaro partition. When I try loading the system it doesn’t seem to work, I must have messed something up.