Yea, I have to agree with S.B. I do exactly what he does, the filler blank looks great, it only takes 20 minutes or so, and there is no blueing or reblueing involved. You guys are making this way too complicated!
I have also made a slot filler, just like the one shown in the prior post, by taking a rear sight tangent sight, cutting off the end that contains the sight (using a hack saw), grinding that end into a mild point on my bench grinder, cold bluing the fresh cut edges, and putting that in the slot. This takes about 30 minutes and looks great.
Regards,
Mannyrock