My iCloud is full (5GB free plan) and I do not want to pay monthly. I have a Windows 11 laptop. How do I make a full backup of my iPhone onto the laptop?

On Windows 11 install the "Apple Devices" app from the Microsoft Store (on Windows 10 use iTunes instead). Then:

1. Connect the iPhone with a cable and unlock it.
2. Tap "Trust" on the phone and enter your passcode.
3. Open Apple Devices, select your iPhone and go to General.
4. Under Backups choose "Back up all of the data on your iPhone to this computer".
5. Tick "Encrypt local backup" and set a password. Write that password down, it can not be recovered.
6. Click Back Up Now.

Encrypting is worth it because only an encrypted backup includes saved passwords, Wi-Fi settings and Health data.

Done. Where is the backup stored? And can I open it to see my photos?

The backup lives in a folder under your user profile (for the Microsoft Store version it is %userprofile%\Apple\MobileSync\Backup). It is not meant to be opened by hand, the files have random names. It is only useful for restoring to an iPhone.

For photos, plug in the phone and open File Explorer > This PC > Apple iPhone > Internal Storage > DCIM. You can copy the photos and videos from there like normal files. Do that as well as the backup.

Photos copied and the full backup is done. Thanks Kerry, saved me a subscription.