When do you score bread?

"At what point do you score it?"

Score it right before the oven, after the final proof. That timing is the whole trick, and it is where a lot of home loaves go sideways here in Canada too, especially in winter when proofing runs long and it is tempting to get the cutting done early.

Do not score it any earlier. Any cut you make before the loaf is ready just seals back over while it proofs, so by the time it bakes there is nothing left to open up. Wait until the loaf is fully proofed and ready to bake, then use a sharp lame so the cut stays clean and go about a quarter inch deep. Then get the loaf into the oven straight away, before that cut has a chance to close up again.

Asked on r/Breadit

Watch the 30-second version: