How about: "Young man/lady, there are starving children in Africa
who'd love any bread at all, let alone crookedly sliced bread"?
Seriously though, I'd start with a good bread knife. My bro gave me
one of those J.A.Henckel-type bread knives for Xmas and I did not
know how sucky my old knife was until I used the new knife.
Secondly, when slicing, as with driving and sewing, don't look at
where you are right now but instead look at where you want to
be. Just as you would not be looking at the road right in front of
the car but rather keep your sight higher up towards the horizon,
look at where you want the blade to end up not where the blade is
RIGHT NOW. Try that and see if it helps.
Andy Nguyen