A few practical options:

1. Use a tripod with an inverted or reversible center column. Many tripods let you hang the camera below the tripod head so it can sit much lower without you having to squat.

2. Shoot from a higher position and correct perspective afterward. If you can’t get perfectly level with the stone, take the photo from above and use perspective correction in post-processing to make the sides appear parallel. This is often easier and can work very well.

3. Use tethered shooting. Put the camera on a low tripod and connect it to a laptop so you can preview composition and trigger the shutter remotely without crouching.

As for focusing on a camera mounted away from you: tethered shooting is the easiest solution if your camera supports it. Otherwise, set up the shot on a tripod first, use autofocus or manual focus, and then trigger the shutter with a remote or self-timer.

A phone-style selfie stick generally isn’t the best solution for a regular camera because stability and framing become difficult.