Witch/18th

Effortless Concentration

At 18th level, you learn to maintain some magic effects without concentration. When you cast a witch spell of 3-points (2nd-level) or lower which normally requires concentration, you need not concentrate on it. When you cast such a spell, you can choose for it to last for its full duration without your concentration, freeing you to concentrate on another effect instead.

A spell doesn't gain this benefit if you cast it with more than 3 magic points (or cast it with a spell slot higher than 2nd), nor if it's a spell which doesn't appear on the Witch Spell List.

Your Flying Broom feature no longer requires concentration to persist.