how to recover spell slots
Spellcrux Amulet - bg3.wiki
The amulet can recover spell slots that the caster does not innately have from their class, such as ones gained from Create Spell Slot, or ones from gear, such as Shield of Devotion.
Ritual Spells in D&D 5e | Save Your Spell Slots! - Tabletop Joab
Spell Slots The Bard table shows how many spell slots you have to cast your spells of 1st level and higher. To cast one of these spells, you must expend a slot o f the spell’s level or higher.
The Abacus | Talesmith Tavern
Druids of the Land subclass recover a number of spell slots equal to half their level (rounded up). This only occurs on the first Short Rest of the day.