The new Cartomancer feat from The Book of Many Things has a feature, Hidden Ace, that says "when you finish a long rest, you can choose one spell from your class's spell list and imbue that spell into a card." After this you can "you can use a bonus action to flourish the card and cast the spell within."
It could be compared to the magic items wand of magic missiles and rod of resurrection, in that it does not mention anything about spell slots:
While holding it, you can use an action to expend 1 or more of its charges to cast the magic missile spell from it.
While you hold it, you can use an action to cast one of the following spells from it: heal (expends 1 charge) or resurrection (expends 5 charges).
It could instead be compared to feats like Fey Touched which do mention "without using a spell slot":
You learn the Misty Step spell and one 1st-level spell of your choice. [...] You can cast each of these spells without expending a spell slot.
I thought the operative difference between the wand of magic missiles and the Hidden Ace feature might be the phrase "from it." In that case, Cartomancer would not allow you to cast the spell from the imbued card, it allows you to cast the spell (by expending a spell slot). However, the ring of spell storing does not use the phrase "from it" and implies you cast the spell, while not requiring the expenditure of a spell slot when casting.
While wearing this ring, you can cast any spell stored in it.
So, does the imbued card from Cartomancer's Hidden Ace feature allow you to cast the imbued spell without expending a spell slot (as wands, rods, and rigns do), or must you expend a spell slot because it doesn't say otherwise (as other feats do)?