GA pilot reported taxiing on to the runway at 7B3 in the path of a landing aircraft that he had overlooked. The aircraft on approach executed a go-around.

Narrative

The hold short line to Runway 20 at 7B3 is about what you'd expect on the east taxiway; but the west taxiway approaches the runway at a shallow angle and the hold short line is farther back. At this west hold short line; trees obscure the downwind leg past the numbers and the base leg.I was holding here as I did my pre-takeoff checks; checking the pattern when I stopped and trying to be aware of the pattern as I worked. Before I pulled forward to take the runway; I looked and vocalized 'final is clear.' About halfway from the hold short line to the end of the runway I saw an aircraft established on final. Realizing that trying to make a 180 and rush back to the hold short line again might cause extra trouble; I pulled ahead to the corner of the pavement. I stopped in a spot north (on the approach side) of the displaced threshold and wide of the runway edge; and I turned so I could keep an eye on the approaching aircraft. This was as out of the way as I could be; but I was still fouling the runway and the traffic went around. Separation remained good and there was never any risk of collision.The ceiling and visibility were unlimited.The root cause is clear: I didn't do a good enough job of clearing the approach path before entering the runway.Contributing to this was complacency. I probably expected final to be clear since I hadn't detected traffic as I was holding short. But being vaguely aware of the pattern as I'm doing something else clearly isn't sufficient to detect traffic in the pattern.Also contributing was my expectation of where traffic should be in the pattern. I was flying a Aircraft X and making tight patterns; while the traffic was low on a relatively long final. I'll now broaden where I look for traffic.I think I did a fair job of resolving the issue in the moment; and deciding not to return the way I came was correct. But in hindsight I could have crossed the centerline and across the closer hold short line on the east taxiway. This is not a situation I have ever briefed; even with an instructor; but there's no reason not to. We make a point of checking final before entering the runway; so I can't claim to be ignorant of the risk. In the future I'll try to explicitly identify and think through risks more.