A few thoughts...
Having done many new break ins on engines, this was the guidance given by very experienced Engineers.
Run for 1 hour hard, as per schedule for break in.
Drop the oil and change the filter.
That gets rid of any storage oil residue, bits and pieces, rocks and stones leftover from the build
Run hard for 5 more hours, do the same.
Then run until oil consumption stabilises at which point, swap to a good multigrade and enjoy a long and healthy engine life
Caveat: I'm not an expert, but that's rarely stopped me from having an opinion.
+1 on the above, with a few suggested additions/clarifications.
First and foremost, make sure that you know what oil is in there now. If it's storage oil, dump and replace it before proceeding further.
If it's been 6+ months, it's likely that oil is largely gone from cylinder walls. Just before starting, remove all spark plugs. Position a piston to BDC, spray in some sort of light oil through both top and bottom plug holes. Wash, rinse, repeat... for other cylinders. Replace and torque plugs, take a last look at everything, button up and go.
Other minor thoughts that come to mind wrt Mike's procedure are:
1) At the one hour oil change, I don't know how much value there is in changing the filter. Anything trapped there is presumably going to stay. Certainly however, it can't hurt to do so, other perhaps than scaring yourself with the stuff that you see when you open and inspect it.
2) Probably implied in Mike's note, but if not, be sure to remove, inspect, clean, and reinstall (with new crush gasket and safety wire) the suction side oil screen. Even if not changing the filter, I'd do this at one hour mark, as some of the stuff captured there could later get through depending on shape and orientation.
3) I'd probably let CHTs and (if you can determine it over such a short window) oil consumption guide me as to whether to do the second change at 5 hours, or possibly until 10. Basically the idea would be to have confidence that the break-in was largely complete before the second change.