I have tried several ways of leveling my bed and have found this the best for me.
I first get it close using the paper method then I print a very simple one layer print just a square 100mm outside and 80 mm inside with one corner rounded off and a small v shape on one side. This shape allows me to know how it was on the bed when printed. Once printed, I measure the thickness with a pair of calipers. After a few prints I can get the hole print within .02mm.