I ended up figuring it out after realizing the freeze wasn't actually a freeze and just a very long load time. I would've tried going up and sliding earlier but in my first playthrough I was afraid of it crashing lol.
So with that in mind I think that there still needs to be some kind of hint towards the slide being used as an attack. I know you have that for the doors, but maybe if you added some destructible boxes or something to slide through it could reinforce that. (that first slide tutorial is a prime spot for it imo)