Does Aluren allow you to cast creature spells with flash at instant speed for free?

Aluren reads: 'Any player may cast creature spells with mana value 3 or less without paying their mana cost and as though they had flash.' The enchantment independently grants two benefits: (1) the creature can be cast without paying its mana cost, and (2) it can be cast at instant speed (as though it had flash), as per CR 702.8 (flash) and the interaction with CR 601.3 on timing permissions.

Because Aluren itself grants the flash-like timing permission to all eligible creatures, a creature that already has flash gains no extra benefit from Aluren in terms of timing — both routes arrive at the same outcome: the ability to cast at instant speed. The two effects simply overlap harmlessly (CR 112.6a).

The 'without paying its mana cost' clause is governed by CR 601.2b, which allows a spell to be cast without paying its mana cost when a permission explicitly says so. Additional costs (like kicker) can still be paid on top, but the mana cost itself is zeroed out.

Concrete example: You control Aluren and want to cast Ambush Viper (a 2-mana creature with flash and deathtouch). Because its mana value is 2, you may cast it during your opponent's combat step — for free — even if it lacked flash, because Aluren provides both the cost reduction and the timing permission.

Note: Aluren is a 'may' ability, so you are never forced to use it. You could still cast an eligible creature the normal way if you preferred (e.g., to avoid giving opponents the same option).