I bet some of that is just because you're more used to Windows. Plus, if you compare using a graphical program for Windows with using linux from a terminal, Windows wins hands down. If you compare doing it Windows from C:\ instead, I bet they stack up pretty equally ...i.e. both ways are tuff if you aren't used to them.
Here's my recommendation for doing it in Linux without having a PhD., and using only the tools you already have. This assumes you still have the Mint live USB that you used to install Mint on your new build:
1. Boot from the live USB..Using the live USB avoids any potential isssues with trying to image the disk the OS is on while you're using it. Linux is generally pretty picky about doing stuff like that to the disk the OS is on while the OS is running. So easiest to boot from the Live USB.
2. Open "Disks" from the menu. I'm not sure what sub-menu its in with Mint (in Ubuntu Mate its in "Preferences", but in Mint it may be "Accessories"?)
3. Identify the disk you recently installed Mint on (or Mint and Windows if you did both) that you want to create an image of. Click on the disk in the left hand pane.
4. Click the "more" icon"(the 3 stacked elipses) and select "Create Disk Image".
5. Name the image, and pick where to save it. If you're saving it to a second hard drive in your system or external drive, you may want to check ahead of time that its mounted in the live session. You can check that, and mount the destination drive if necessary, right there in Disks. The Mint live USB will often auto-mount all the disks it finds, but best to check.
6. Click "Start Creating" or "Start", or etc. If you've got a sizable install....it could take a while, but you'll get a progress bar.
Pictures here are just for reference. It may look a bit different for you as I'm on Ubuntu Mate, but its the same underlying program:
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Not overly hard, eh? Sometimes I think that there'd be more people adopting desktop Linux if more tutorials referred to available graphical tools. After all, there's always a lot of tutorials on how to do things in Linux from the terminal, while almost nobody publishes tutorials on how to accomplish things in Windows from the command prompt.