...and yet they are pronounced very differently.
/ˈslɔtər/ vs /ˈlɑːftə(r)/ For those who don't read 'pronunciation': Slaw-ter vs Laff-ter
Similarly: Homographs (words spelled identically but pronounced differently) run into the same issue for an English language learner.
Examples:
After weeks in the desert the troops began to desert their fellows.
You can lead someone into a dark alley and then club them with a lead pipe.
She wound the bandage around his head wound (after he was hit with a lead pipe for deserting his fellows).
What is the best way to explain to a learner of English why the pronunciation differences exist and how to avoid the trap presented by homographs and other near-homographs (like s/laughter)?