Neck flexion — trains the front/sides of the neck. You already do these. Builds a strong, athletic, injury-resistant neck.
Cues
Lie face-up, head off the bench, plate on the forehead with a towel or beanie (it's uncomfortable bare), curl the chin toward the chest through full range, lower slowly.
Programming
2–3 × 12–20. ⚠️ Always do light/bodyweight warm-up sets first.
How to progress
The book: progress reps to ~20 before adding weight; then 8–12 with load, or just keep reps high. → Progression