At that size those have to be one of Amorphophallus titanium’s smaller cousins, probably A. Konjac (I grow those).
A. titanium used to be unobtanium, found only in a few major greenhouses. But sometime around 20 years back someone had a fertilized flower that produced hundreds of seeds and started selling seedlings for around $100 each. You can buy one (of unspecified size in a 3.5 inch pot) for $85 today.
The only reason I never bought one is because I don’t live in a warm enough climate or have a suitable greenhouse/hothouse. If did and bought one when they were first available I probably would have had at least a couple of blooming years by now.
Amorphophallus species have staggered maturation of the flowers so that on a single plant the female flowers aren’t receptive when the male flowers are producing pollen. But if you have at least two blooms a few days out of synch with each other you can end up with a stalk covered with hundreds of seeds. And they spread rapidly from outgrowths of the roots. So once you have successful growing conditions for an Amorphophallus, you basically become an Amorphophallus factory.