If you spend your time removing seeds and the core from a capsicum before cutting it, Reddit user mechanical_fungineer suggests a far simpler method: cut around the core and skip those steps entirely.
Start by cutting off the top and bottom of the capsicum and then cut away the sides. What you're left with is the core and seeds all stuck together in a nice, clean structure. You won't have to worry about cleaning up the seeds that have fallen everywhere or cutting up the core. (Oz editor note: I've always cut capsicum this way, but I know from experience many people don't. Definitely worth the time saving!)