Arcane Circle

As you cast the spell, a 10-foot-diameter visible circle centred around you appears on the ground. If the spell is cast in the air, the user must maintain the same position, or the spell dissipates. The circle does not move with the user. It lasts for 1 minute or until the a part of the caster's body does not touch the circle anymore.

Any creature within the range of the circle can cast spells up to 7th level without expending a spell slot on any of them. A lower level spell that is upcasted to a higher level does not consume a spell slot as long as it does not exceed 7th level. If you use a variant spell points system, a creature cannot use more than 10 spell points to cast a spell. Any amount of creatures can benefit from this spell, as long as they stay inside it.

The spell takes effect only after it was cast, meaning it still consumes a spell slot as long as it was not cast while under the effect of another Arcane Circle.