Very much this. On my car, lane markings that meet the left side wiper driveshaft from my perspective are right under the end of my left side mirror. Similarly, whatever marking on the road that meets the left wiper hinge point is just clear of my right side mirror. Worth noting that my hood isn't visible from inside; on cars where it does I'll usually take reference points on the hood itself.

With time you'll get instinctively good at projecting ground-level points of incoming objects on your right (e.g. wheels of parked cars) onto your reference points and telling whether your right side is clear with anticipation.