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I have yet to reach the skill level while sharpening freehand that I can consistently avoid rounding-over the edge when engaged in that particular pursuit... ,,....
To avoid rounding over is very easy; you simply
choose not to do it.
Instead you
choose to do the opposite. Could call it "rounding under"!
Start your pass with the tool at the chosen angle (usually 30º) and as you thrust it forwards over the stone you dip it very slightly, to end up at a slightly lower angle.
The edge gets honed at 30º at the start of the pass but as you go forwards the back of the bevel gets taken off at a slightly lower angle - what modern sharpeners would call the primary bevel, but slightly rounded convex.
Might sound tricky but it takes a few seconds to get the idea and becomes natural and easy.
It's very much easier than trying to hone a flat bevel, which doesn't serve any purpose anyway.
It is
the way in to freehand sharpening. The other essential is to bring up a burr. If it doesn't happen quickly don't waste your time, go on to a coarser stone. Then back to finer - as fine as you want, plus stropping if you want scary sharp.
For most ordinary purposes the Norton India "medium" grit is good enough.
So it's three things:
rounding
under (very slightly):
bringing up (and taking off) a burr:
a little and often (never let the edge go blunt).