[Stick486]

use a speaker magnet to hold the chisel or the like...
paint the back of the chisel w/ a felt tip.. (when you are flat the felt tipping will be gone)...
use a circular motion on your stone..
every time you change grits, change the direction of the motion..
you only need to flatten the 1st half to 2/3rds of the chisel...

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[Stick486]

@JOAT

The importance of flattening the back of the chisel is to make sure the knife edge, after sharpening the bevel, has a straight edge...see pic below...

Imagine if the back were not flattened (gray area in the pic)...the sharpened edge would not be straight.

that chisel appears to be a cranked neck and the way the flattening came out it is perfect for using it for paring...

 

[Stick486]

According to Lee Valley who sell the Narex chisels up here they are supposed to come flatter than that. I've taken literally hours to get some of the old Sheffield chisel makers chisels flat across the bottoms. I used to quit when I got to 600 grit on my diamond stones but then I tried some 2500 grit carbide paper on glass and there was a noticeable improvement.

the more polished the back side the less friction there helping the chisel cut easier/smoother...

 

[Stick486]

I use the side of the wheel on my Tormek for flattening...
I get a mirror in a few minutes...