Paladin/Warlock multiclass (max lvl either 11 or 14)
Depleted spell slots are generally replenished by taking a Long Rest (Short Rest for Warlocks), though there are methods of creating additional slots, or replenishing expended ones.
Realistic Short Rest - Resurrected at Baldur's Gate 3 Nexus - ...
Warlocks specifically use Warlock Spell Slots that can be replenished upon a Short Rest. Clerics and Wizards have regular Spell Slots that can only be replenished by having a Long Rest at camp.
Resting - bg3.wiki
A Paladin X/Warlock 2 will get a couple key invocations (like the devil sight trick) and will recharge their two highest paladin spell slots on a short rest, for divine smite or for whatever other purpose.
spell-slots-wizard - ttytcammy.vn
Once per day when you finish a short rest, you can choose expended spell slots to recover that have a combined level equal to or less than half your wizard level (rounded up).