If you frequent these forums and have recently purchased the Amazon Fire HD 10 chances are you have at least tried to modify it to get the Google Play Store involved. If you are a bit more of a tinkerer you may have decided to change the OS altogether opting to run a custom rom like CyanogenMod. If you flash the wrong thing accidentally you can end up with a bricked device. You will want to know how to restore the device to stock firmware in case something like this happens.
First you will need to download the firmware from the link below, install ADB and Fastboot to your PC, Power off the Fire HD 10 and be sure it is unplugged, boot into stock recovery (Press and hold volume down+power for 5 seconds, select stock recovery, select apply update from adb, plug your device into PC usb, open up your fastboot and adb folder be sure this is where the stock image is located, inside the folder right click and select "open command prompt here", check that the PC sees your device "adb devices", to install the stock image type the command "adb sideload update-kindle-32.5.2.2_user/522054520.bin" (you could actually rename the file to make things simpler). Once the flash finishes you can reboot your device.
Amazon Fire HD 10 Stock Image