Slicing the hot dog bun is a standard part of it’s preparation and presentation. Not really part of this.

And if you were presented a “Slice of pie” as A thing. It would in fact be a Taco.
However If you were presented a whole pie and decided to slice it to eat it. “The Pie” would still be a 5 or 6. “The Slice” would be a 3. “The Pie” didn’t change by having a slice removed.

Does that distinction make sense? “A Pie” is one thing. “A Slice of Pie” is a different thing.