Is it interference = two penalty throws?
810 Interference E:
E A player who intentionally interferes with a disc in any of the following ways receives two penalty throws:
1 Altering the course of a thrown disc (other than to prevent injury); or,
2 Moving or obscuring a thrown disc or marker disc (other than in the process of identification, retrieval, marking, or as allowed by 810.H).
Ok, so yes, if a player interferes with a thrown disc . But what is a Thrown disc?
802.01 Throw
A. A throw is the propulsion and release of a disc in order to change its position. Each throw that is made as a competitive attempt to change the lie is counted.
So, for it to be a throw you must release the disc in a competitive attempt to change the lie.
Rules Questions and Answers
THROW
QA-THR-1: My throwing hand bumped a tree branch during my backswing, knocking the disc to the ground, and the disc rolled forward of my lie. Was that a throw?
No. A throw begins when the disc is moving forward in the intended direction. A disc dropped or knocked out before or during a backswing does not count as a throw.
And to clarify the disc must have started moving forward in the intended direction (So as to the previous discussion of forward with patent pending, the whole sentence is not only forward, but forward in the intended direction)
So, to be a throw you have to release the disc in a competitive attempt to change the lie and the disc must have started moving in the intended direction.
My take on the situation in the example in the OP is that when the disc is tossed straight up in the air, this is not a "throw" since it a, did not start moving in the intended direction (towards the basket) and b, it was not a compentitive attempt to change the lie.
I would compare this with someone standing with a disc in their hand and just throwing it up an catching it a couple of times, like many players do both while waiting and also before making a put.
If the disc being tossed straight up in the air is not a "throw" you won't get two penalty throws, because there hasn't been a thrown disc to interfere.
So is slapping a disc a allowed way to make a throw?
Rules Q & A
QA-THR-2: Are there any restrictions on how you throw the disc? For example, can you throw nothing but overhand shots?
There are no restrictions on how you throw the disc. You may throw backhand, sidearm, overhand, thumber, or any other way that occurs to you. You can throw it with your foot if you want.
This isn't totally clear to me. But it says there is not restriction on how you throw the disc and that a throw is a"propulsion and release of a disc in order to change its position".
I can't say for sure that the rules don't allow you to push or hit a disc to make a valid throw according to the current rules.
801.03 Appeals
A. When a group cannot reach a majority decision regarding a ruling, the ruling is based on the interpretation that is most beneficial to the thrower.
"When in doubt, go with the thrower" would make me to accept a throw like this under the current rules if someone can't show me some other part of the rules than the above that disallows it.
I would however not recommend a "slap putt" and would welcome some kind of additional wording in the rules or a Q&A addition that wouldn't allow it. But as my conclution as to the above I can't find any support in the current rules to not allow it.
*Edits to correct spelling and grammar errors since English isn't my first language.*